Tetraruthenium Metallamacrocycles with Potentially ... - MDPI

inorganics Article

Tetraruthenium Metallamacrocycles with Potentially Coordinating Appended Functionalities Patrick Anders

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, Mario Robin Rapp, Michael Linseis and Rainer F. Winter *

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Fachbereich Chemie der Universität Konstanz, Universitätsstraße 10, D-78457 Konstanz, Germany; [email protected] (P.A.); [email protected] (M.R.R.); [email protected] (M.L.) * Correspondence: [email protected]; Tel.: +49-7531-88-5355

Received: 26 June 2018; Accepted: 20 July 2018; Published: 24 July 2018

Abstract: We present four new tetraruthenium macrocycles built from two 1,4-divinylphenylene diruthenium and two isophthalic acid building blocks with peripheral, potentially mono- or tridentate donor functions attached to the isophthalic linkers. These macrocycles are characterized by multinuclear NMR spectroscopy, mass spectrometry and, in the case of the thioacetyl-appended complex 4, by X-ray crystallography. Cyclic and square wave voltammetry establish that the macrocycles can be oxidized in four consecutive redox steps that come as two pairs of two closely spaced one-electron waves. Spectroscopic changes observed during IR and UV/Vis/NIR spectroelectrochemical experiments (NIR = near infrared) show that the isophthalate linkers insulate the electroactive divinylphenylene diruthenium moieties against each other. The macrocycles exhibit nevertheless pronounced polyelectrochromism with highly intense absorptions in the Vis (2+/4+ states) and the NIR (2+ states) with extinction coefficients of up to >100,000 M−1 ·cm−1 . The strong absorptivity enhancement with respect to the individual divinylphenylene diruthenium building blocks is attributed to conformational restrictions imposed by the macrocycle backbone. Moreover, the di- and tetracations of these macrocycles are paramagnetic as revealed by EPR spectroscopy. Keywords: ruthenium; metallamacrocycle; electrochemistry; spectroelectrochemistry

1. Introduction We have recently reported on some representatives of new types of metallamacrocyclic ruthenium complexes based on alkenylarylene and carboxylate linkers [1–4], which add to the rapidly growing class of redox-active metallamacrocycles [5–7]. Metallacycles of type I in Figure 1 are constructed from bis(alkenyl)arylene diruthenium complexes and isophthalic acid derivatives or pyridine-3,5-dicarboxylate as two different kinds of building blocks [1,2,4]. Metallacycles of type II, in contrast, are made from self-complimentary building blocks that incorporate the alkenylarylene and the carboxylate functionalities within the same bridging ligand [3,4]. A feature common to both types of macrocycles is their redox activity with one reversible one-electron oxidation per alkenyl ruthenium moiety. By peripherally appending triarylamine tags, their redox activity can be even further enhanced to the reversible loss of up to eight electrons per macrocycle [2]. Despite this unifying principle, ruthenium macrocycles of types I or II strongly differ with respect to the pattern of the individual redox waves and their properties. Thus, members of the type I family are characterized by two pairs of closely spaced one-electron voltammetric waves that are mutually split by ca. 300 mV, representing the stepwise oxidation of first the one and then the other divinylarylene diruthenium moiety to their associated radical cationic (first pair of waves) and then to the dicationic states (second pair of waves). The spatial extension of the π-conjugated metal-organic pathway renders tetraruthenium macrocycles of this architecture highly efficient polyelectrochromic Inorganics 2018, 6, 73; doi:10.3390/inorganics6030073

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dyes organic [8–12]. Another property is the paramagnetism of architecture the di- and tetraoxidized forms, pathway interesting renders tetraruthenium macrocycles of this highly efficient which feature two or four uncoupled spins, even in the presence of 1,4-divinylphenylene linkages polyelectrochromic dyes [8–12]. Another interesting property is the paramagnetism of the di‐ and [1]. Tri- or tetraruthenium of two family however, offer three or four individually tetraoxidized forms, macrocycles which feature or II, four uncoupled spins, even in the presence of resolved, 1,4‐ ratherdivinylphenylene linkages [1]. Tri‐ or tetraruthenium macrocycles of family II, however, offer three evenly spaced, consecutive one-electron redox waves in electrochemical experiments. Moreover, four individually resolved, rather evenly spaced, redox constituents waves in in they or show clear signs of electronic coupling between theconsecutive individual one‐electron monoruthenium electrochemical experiments. Moreover, they show clear signs of electronic coupling between their mixed-valent +/2+ or +/2+/3+ states as revealed by the presence of weak intervalencethe charge individual monoruthenium constituents in their mixed‐valent +/2+ or +/2+/3+ states as revealed by transfer (IVCT) transitions. They thus resemble electrically conductive molecular loops. This, however, the presence of weak intervalence charge transfer (IVCT) transitions. They thus resemble electrically comes at the expense of a significantly attenuated performance as polyelectrochromics, [13–19] due conductive molecular loops. This, however, comes at the expense of a significantly attenuated to fact that the π-conjugated chromophores are restricted to just a monoruthenium alkenylarylene performance as polyelectrochromics, [13–19] due to fact that the π‐conjugated chromophores are building block. restricted to just a monoruthenium alkenylarylene building block.

Figure 1. Vinylarylene‐bridged ruthenium macrocycles of types I and II.

Figure 1. Vinylarylene-bridged ruthenium macrocycles of types I and II.

One formidable challenge en route to responsive materials made from such macrocycles is to interconnect individual molecules to larger, ordered arrays [20]. Assembling individual macrocycles One formidable challenge en route to responsive materials made from such macrocycles is to via coordinative or molecules covalent bonds or other specific intermolecular interactions might macrocycles ultimately via interconnect individual to larger, ordered arrays [20]. Assembling individual provide more complex structures with anisotropic electrical or electronic properties, if the type of coordinative or covalent bonds or other specific intermolecular interactions might ultimately provide morebonding interactions between individual macrocycles differs for different directions in space. Such a complex structures with anisotropic electrical or electronic properties, if the type of bonding level of structural complexity would go beyond that of traditional MOFs. As a first step to such interactions between individual macrocycles differs for different directions in space. Such a level of materials, we here report on four new tetraruthenium macrocycles of type I with either terpyridine‐ structural complexity would go beyond that of traditional MOFs. As a first step to such materials, (terpy), 1,3‐(dipyrid‐2‐yl)phenyl‐(phpy2), (4‐ethynylpyridine)‐ or 4‐thioacetyl‐functionalized we here report on four new tetraruthenium macrocycles of type I with either terpyridine- (terpy), isophthalate linkers along with their electrochemical and spectroscopic properties. 1,3-(dipyrid-2-yl)phenyl-(phpy2 ), (4-ethynylpyridine)- or 4-thioacetyl-functionalized isophthalate 2. Results and Discussion linkers along with their electrochemical and spectroscopic properties. As the functionalized isophthalate linkers of this study we employed 2,6‐di(pyrid‐2‐yl)‐ pyridine‐3,5‐dicarboxylate (IL1), the 3,5‐bis(pyrid‐2‐yl)phenylethynyl‐appended isophthalate IL2, the the 5‐ethynylpyridine‐appended isophthalate IL3, 5‐thioacetyl‐modified isophthalate IL4 (see As functionalized isophthalate linkers of thisand study we employed 2,6-di(pyrid-2-yl)-pyridineFigure 2). IL1 was already in 1961 and made by condensation of picolinoylacetate 3,5-dicarboxylate (IL1), the reported 3,5-bis(pyrid-2-yl)phenylethynyl-appended isophthalate with IL2, the ammonia followed by oxidation of the cyclic 1,4‐dihydropyridine with nitrosulphuric acid 5-ethynylpyridine-appended isophthalate IL3, and 5-thioacetyl-modified isophthalate and IL4 (see subsequent basic hydrolysis of the formed diethyl ester [21]. In our present work we employed Figure 2). IL1 was already reported in 1961 and made by condensation of picolinoylacetate with permanganate oxidation of 3′,5′‐dimethyl‐2,2′,6′,2′′‐terpyridine [22] to prepare the dimethyl ester of ammonia followed by oxidation of the cyclic 1,4-dihydropyridine with nitrosulphuric acid and IL1. The latter was saponified in situ before macrocycle synthesis. Linkers IL2 to IL4 are new. IL2

2. Results and Discussion

subsequent basic hydrolysis of the formed diethyl ester [21]. In our present work we employed permanganate oxidation of 30 ,50 -dimethyl-2,20 ,60 ,200 -terpyridine [22] to prepare the dimethyl ester of IL1. The latter was saponified in situ before macrocycle synthesis. Linkers IL2 to IL4 are new. IL2 was made by Sonogashira coupling of 1-bromo-3,5-di(pyrid-2yl)benzene [23] with 5-ethynylisophthalic

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was made by Sonogashira coupling of 1‐bromo‐3,5‐di(pyrid‐2yl)benzene [23] with 5‐ acid dimethyl ester. The latter was prepared bywas a Sonogashira of the reaction corresponding ethynylisophthalic acid dimethyl ester. The latter prepared by reaction a Sonogashira of the 5-bromo derivative with trimethylsilylacetylene (TMSA) followed by deprotection of the product corresponding 5‐bromo derivative with trimethylsilylacetylene (TMSA) followed by deprotection of with K2 CO3 /MeOH. Sonogashira coupling of 5-ethynylisophthalic acid dimethyl ester with the the product with K2CO 3/MeOH. Sonogashira coupling of 5‐ethynylisophthalic acid dimethyl ester hydrochloride of 4-bromopyridine afforded linker IL3. IL4 was prepared from acetylation of the with the hydrochloride of 4‐bromopyridine afforded linker IL3. IL4 was prepared from acetylation known 5-mercaptoisophthalic acid [24] with acetic acid anhydride. Details of the synthesis and the of the known 5‐mercaptoisophthalic acid [24] with acetic acid anhydride. Details of the synthesis and characterization of IL1 to IL4 and of new synthetic intermediates are given in the Experimental the characterization of IL1 to IL4 and of new synthetic intermediates are given in the Experimental Section. NMR spectra of all all new new isophthalate isophthalate ligands ligands are are collected collected as as Figures Figures S1 S1 to to S8 S8 in in the Section. NMR spectra of the Supplementary Materials. Supplementary Materials.

Figure 2. Ligands IL1 to IL4 and the derived tetraruthenium macrocycles 1–4. Figure 2. Ligands IL1 to IL4 and the derived tetraruthenium macrocycles 1–4.

The four new tetraruthenium macrocycles 1–4 shown in Figure 2 were generated in yields of The four new tetraruthenium macrocycles 1–4 shown in Figure 2 were generated in yields of 46% to 87% by stirring equimolar amounts of the divinylphenylene‐bridged diruthenium complex 46% to 87% by equimolar amounts of the divinylphenylene-bridged diruthenium complex iPrstirring {Ru(CO)Cl(P 3)2}2(μ‐CH=CH–C6H4–CH=CH‐1,4) [8] and the respective isophthalate linkers IL1 to i {Ru(CO)Cl(P Pr3 )2 }22(µ-CH=CH–C 6 H4 –CH=CH-1,4) [8] and the respective isophthalate linkers IL1 to IL4 in a MeOH/CH Cl2 mixture (ca. 1:1, vol:vol), subsequent filtration of the soluble materials over IL4 in a MeOH/CH Cl mixture (ca. 1:1, vol:vol), subsequent filtration of the soluble materials over 2 2 Celite®, and washing of the solid residue that remained after removal of the solvents with methanol, ® Celite , and washing of the solid residue that remained after removal of the solvents with methanol, ether and pentane. Reaction times varied between 3 h and 3 days. In the latter cases, monitoring of ether and pentane. Reaction betweenrevealed 3 h and the 3 days. In theof latter cases, monitoring the reaction solutions by 31P times NMR varied spectroscopy presence several species during 31 P NMR spectroscopy revealed the presence of several species during of the reaction solutions by intermediate stages of the reaction. These multicomponent mixtures gradually turned uniform, intermediate stages of the reaction. These multicomponent mixtures gradually turned uniform, leaving leaving just one principal, dissolved species besides variable quantities of insoluble, solid material at just one principal, dissolved species besides variable quantities of insoluble, solid material at the end of the end of the reactions. The success of these self‐assembly reactions obviously rests on the reversible the reactions. The success of these self-assembly reactions obviously rests on the reversible binding of binding of the carboxylate linkers and a thermodynamic competitiveness of the cyclic architectures the carboxylate linkers and a thermodynamic competitiveness of the cyclic architectures with respect with respect to linear, polymeric structures due to enthalpy‐entropy compensation [25–27] and the to linear, structures due to enthalpy-entropy compensation [25–27]of andequilibria the stabilities of the stabilities polymeric of the as‐formed macrocycles [28–30]. Similar observations involving as-formed macrocycles [28–30]. Similar observations of equilibria involving reversible ligand binding reversible ligand binding en route to closed metallamacrocycles were reported on earlier occasions, en route to closed metallamacrocycles were reported on closed earlier macrocycles occasions, including diruthenium including diruthenium complexes [31]. However, even may undergo ligand complexes [31]. However, even closed macrocycles may undergo ligand scrambling in scrambling in the presence of an excess of a ditopic ligand [30,32,33]. Gratifyingly, the the presence angular of an excess of a ditopic ligand [30,32,33]. Gratifyingly, the angular dispositions of the coordinating dispositions of the coordinating functionalities at the divinylphenylene and the isophthalate linkers ◦ [2,4] functionalities at the andselective the isophthalate linkers of ca. 160◦ and of ca. 1202 of ca. 160° and of divinylphenylene ca. 120° [2,4] grant formation of rectangular, unstrained + 2 grant selective formation of rectangular, unstrained 2 + 2 tetraruthenium macrocyclic structures as tetraruthenium macrocyclic structures as opposed to larger cyclic arrays (vide infra). opposed to larger cyclic arrays (vide infra). The new macrocycles are characterized by the appropriate NMR resonances of the two different The macrocycles characterized by the appropriatediruthenium NMR resonances of and the two kinds of new ditopic building are blocks—the divinylarylene‐bridged complex the different kinds of ditopic building blocks—the divinylarylene-bridged diruthenium complex and the isophthalate linker—in a 1:1 ratio, with distinct peak shifts when compared to the isolated precursors isophthalate linker—in a 1:1 ratio, distinctspectra peak shifts when compared to in thethe isolated precursors (for graphical representations of with the NMR see Figures S9 to S21 Supplementary Materials). As usual, substitution of the chlorido ligand at the ruthenium atoms by a bidentate



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(for graphical representations of the NMR spectra see Figures S9 to S21 in the Supplementary Materials). carboxylate goes along with low‐field shifts of the vinylic protons Ru–CH and Ru–CH=CH and of As usual, substitution of the chlorido ligand at the ruthenium atoms by a bidentate carboxylate those at the 1,4‐phenylene linker by ca. 0.6 to 0.7 ppm, 0.8 to 1.0 ppm, and 0.6 to 0.7 ppm, respectively goes along with low-field shifts of the vinylic protons Ru–CH and Ru–CH=CH and of those at the [1,2,11,34]. Significant shifts are also observed for the protons at the isophthalate ligands, in particular 1,4-phenylene linker by ca. 0.6 to 0.7 ppm, 0.8 to 1.0 ppm, and 0.6 to 0.7 ppm, respectively [1,2,11,34]. for those which are poised to the central cavity. This is exemplified by macrocycle 1 where the Significant shifts are also observed for the protons at the isophthalate ligands, in particular for those corresponding 1H NMR resonance changes from 8.29 ppm in IL1 to 9.80 ppm, or by the 2/IL2 pair of which are poised to the central cavity. This is exemplified by macrocycle 1 where the corresponding compounds, where a shift from 8.65 ppm to 9.28 ppm is observed. Chloride substitution by bidentate 1 H NMR resonance changes from 8.29 ppm in IL1 to 9.80 ppm, or by the 2/IL2 pair of compounds, carboxylate donors is indicated by low‐field shifts of the COO 13C NMR resonances by ca. 10 ppm where a shift from 8.65 ppm to 9.28 ppm is observed. Chloride substitution by bidentate carboxylate when compared to the parent isophthalic esters and, concomitant with the increase of the valence donors is indicated by low-field shifts of the COO 13 C NMR resonances by ca. 10 ppm when compared electron count at the ruthenium atom from 16 to 18, by a 9 cm−1 shift of the CO stretch of the Ru‐ to the parent isophthalic esters and, concomitant with the increase of the valence electron count at the bonded carbonyl ligands to lower energy. ruthenium atom from 16 to 18, by a 9 cm−1 shift of the CO stretch of the Ru-bonded carbonyl ligands While these observations generally confirm the presence of well‐defined macrocyclic structures, to lower energy. they are indeterminate with respect to their nuclearity. Such information can, however, be gleaned While these observations generally confirm the presence of well-defined macrocyclic structures, from the corresponding mass spectra. The latter show clear peaks corresponding to the mono‐ and they are indeterminate with respect to their nuclearity. Such information can, however, be gleaned dications of the intact macrocycles with series of additional peaks corresponding to the stepwise loss from the corresponding mass spectra. The latter show clear peaks corresponding to the mono- and of up to four PiPr3 ligands. In most cases, the mass peak for the [M2+ − 4PiPr3] ion constitutes the base dications of the intact macrocycles with series of additional peaks corresponding to the stepwise peak of the mass spectrum, confirming stability of even the higher oxidized, dicationic states. For loss of up to four Pi Pr3 ligands. In most cases, the mass peak for the [M2+ − 4Pi Pr3 ] ion constitutes preoxidized samples, mass peaks corresponding to even the trications were observed. Figure 3 the base peak of the mass spectrum, confirming stability of even the higher oxidized, dicationic depicts a representative mass spectrum of the ethynylpyridyl‐appended macrocycle 3 and states. For preoxidized samples, mass peaks corresponding to even the trications were observed. demonstrates the excellent match between the calculated and experimentally observed peak Figure 3 depicts a representative mass spectrum of the ethynylpyridyl-appended macrocycle 3 and positions and isotope patterns. Mass spectra of the other metallamacrocycles can be retrieved from demonstrates the excellent match between the calculated and experimentally observed peak positions Figures S22 to S27 of the Supplementary Materials. and isotope patterns. Mass spectra of the other metallamacrocycles can be retrieved from Figures S22 to S27 of the Supplementary Materials.

Figure 3. (Left): HR ESI Mass spectrum of macrocycle 3; (right): experimental (top) and simulated Figure 3. (Left): HR ESI Mass spectrum of macrocycle 3; (right): experimental (top) and simulated (bottom) isotope peak pattern for the [M+ ] peak. (bottom) isotope peak pattern for the [M+] peak.

Final confirmation of the formation of tetraruthenium macrocycles was obtained by an X-ray Final confirmation of the formation of tetraruthenium macrocycles was obtained by an X‐ray diffraction experiment on a single crystal of macrocycle 4 grown from a solution of the complex in a diffraction experiment on a single crystal of macrocycle 4 grown from a solution of the complex in a benzene/MeOH mixture. Details to the data collection, the structure solution and refinement, as well benzene/MeOH mixture. Details to the data collection, the structure solution and refinement, as well as listings of the bond lengths and angles are provided as Tables S30 to S32 in the Supplementary as listings of the bond lengths and angles are provided as Tables S30 to S32 in the Supplementary Materials. Complex 4 crystallizes in the triclinic space group P−1 with two half macrocycles and Materials. Complex 4 crystallizes in the triclinic space group P − 1 with two half macrocycles and eleven benzene solvate molecules in the unit cell. One benzene solvate molecule rests within the inner eleven benzene solvate molecules in the unit cell. One benzene solvate molecule rests within the inner cavity of every macrocycle and, at an interplanar angle of 8.0◦ , is in a close to parallel orientation with cavity of every macrocycle and, at an interplanar angle of 8.0°, is in a close to parallel orientation with the arene rings of the divinylphenylene linkers. the arene rings of the divinylphenylene linkers.

Figure 4 shows front and rear views of an individual molecule of 4 with the numbering of the most important atoms and with the incorporated benzene solvate molecule. The other ten solvate


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Figure 4 shows front and rear Inorganics 2018, 6, x FOR PEER REVIEW

views of an individual molecule of 4 with the numbering of the 5 of 21 most important atoms and with the incorporated benzene solvate molecule. The other ten solvate molecules occupy hydrophobic voids between parallel displaced macrocycle molecules (see Figure S28 molecules occupy hydrophobic voids between parallel displaced macrocycle molecules (see Figure of theof Supplementary Materials). Individual solvate molecules do not display anydisplay notableany interactions S28 the Supplementary Materials). Individual solvate molecules do not notable with each other or the metallamacrocycles. Thus, the shortest C–H ··· C distances between individual interactions with each other or the metallamacrocycles. Thus, the shortest C–HC distances between benzene molecules are 3.0 Å, which is by 0.1 Å longer than what is usually considered as a secondary individual benzene molecules are 3.0 Å, which is by 0.1 Å longer than what is usually considered as bonding interaction. only exception is a exception weak contact 2.638contact Å between one benzene solvate a secondary bonding The interaction. The only is a ofweak of 2.638 Å between one hydrogensolvate atom and atom O1 atom of a carboxylate absence of any intermolecular interactions benzene hydrogen and atom ligand. O1 of The a carboxylate ligand. The absence of any also explains why single crystals of 4 rapidly lose their solvate molecules on removal from the mother intermolecular interactions also explains why single crystals of 4 rapidly lose their solvate molecules liquor. This posed considerable difficulties in collecting a specimen for data collection. Thus, it was on removal from the mother liquor. This posed considerable difficulties in collecting a specimen for necessary to immediately freeze the crystal in a stream of liquid nitrogen in order to avoid a rapid data collection. Thus, it was necessary to immediately freeze the crystal in a stream of liquid nitrogen loss of transparency and crystallinity. Some solvent loss was nevertheless encountered during the in order to avoid a rapid loss of transparency and crystallinity. Some solvent loss was nevertheless X-ray diffraction experiment, even at liquidexperiment, nitrogen temperature. As isnitrogen shown in Figure S29 of the encountered during the X‐ray diffraction even at liquid temperature. As is Supplementary Materials, individual macrocycles weakly associate along the c axis of the unit cell by shown in Figure S29 of the Supplementary Materials, individual macrocycles weakly associate along two c pairs bonding interactions of 2.578 Å and 2.636interactions Å between atom O7 at thioacetyl the axis of of hydrogen the unit cell by two pairs of hydrogen bonding of 2.578 Å the and 2.636 Å i i moiety and methyl protons at the P Pr3 ligands. between atom O7 at the thioacetyl moiety and methyl protons at the P Pr3 ligands.

Figure 4. Two with the the benzene benzene solvate solvate molecule molecule Figure 4. Two different different views views of of an an individual individual molecule molecule of of 4 4 with incorporated into the central cavity. Selected bond lengths in Å: Ru1–P1: 2.398(4), Ru1–P2: 2.413(4), incorporated into the central cavity. Selected bond lengths in Å: Ru1–P1: 2.398(4), Ru1–P2: 2.413(4), Ru2–P3: Ru2–P3: 2.402(4), 2.402(4), Ru2–P4: Ru2–P4: 2.402(4), 2.402(4), Ru1–O1: Ru1–O1: 2.316(6), 2.316(6), Ru1–O2: Ru1–O2: 2.183(6), 2.183(6), Ru2–O3: Ru2–O3: 2.287(6), 2.287(6), Ru2–O4: Ru2–O4: 2.205(6), Ru1–C1: 1.976(9), Ru1–C11: 1.764(10), Ru2–C10: 1.982(10), Ru2–C12: 1.763(10). Selected bond 2.205(6), Ru1–C1: 1.976(9), Ru1–C11: 1.764(10), Ru2–C10: 1.982(10), Ru2–C12: 1.763(10). Selected bond angles in °: P1–Ru1–P2: 179.72(12), P3–Ru2–P4: 176.83(12), O1–Ru1–O2: 58.7(2), O3–Ru2–O4: 59.1(2), angles in ◦ : P1–Ru1–P2: 179.72(12), P3–Ru2–P4: 176.83(12), O1–Ru1–O2: 58.7(2), O3–Ru2–O4: 59.1(2), O1–Ru1–C1: 156.3(3), O2–Ru1–C11: 172.2(4), O3–Ru2–C10: 160.5(3), O4–Ru2–C12: 168.9(4). O1–Ru1–C1: 156.3(3), O2–Ru1–C11: 172.2(4), O3–Ru2–C10: 160.5(3), O4–Ru2–C12: 168.9(4).

While the rather poor quality of the data set in terms of intensity‐to‐noise ratio does not allow While the rather poor quality of the data set in terms of intensity-to-noise ratio does not allow for a detailed discussion of the bond parameters, a qualitative discussion and some statements on the for a detailed discussion of the bond parameters, a qualitative discussion and some statements on macrocycle conformation are nevertheless possible. Of note are the large differences in the Ru–O the macrocycle conformation are nevertheless possible. Of note are the large differences in the Ru–O bond lengths at the bidentate carboxylate linkers. Thus, the Ru–O bonds to the carboxylate O donors bond lengths at the bidentate carboxylate linkers. Thus, the Ru–O bonds to the carboxylate O donors trans to the divinylphenylene ligands (Ru1–O1 = 2.316(6) Å, Ru2–O3 = 2.287(6) Å) are by 0.13 or 0.08 Å longer than those to the oxygen atoms trans to the carbonyl ligand (Ru1–O2 = 2.183(6) Å, Ru2–O4 = 2.205(6) Å). Likewise, the trans‐angles C1–Ru1–O1 and C10–Ru2–O3 of 156.3(3)° or 160.5(3)° show considerably larger deviations from ideality than the angles C11–Ru1–O2 and C12–Ru2–O4 of 172.2(4)° and 168.9(4)° involving the C atoms of the carbonyl ligands. These differences, however, do


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trans to the divinylphenylene ligands (Ru1–O1 = 2.316(6) Å, Ru2–O3 = 2.287(6) Å) are by 0.13 or 0.08 Å longer than those to the oxygen atoms trans to the carbonyl ligand (Ru1–O2 = 2.183(6) Å, Ru2–O4 = 2.205(6) Å). Likewise, the trans-angles C1–Ru1–O1 and C10–Ru2–O3 of 156.3(3)◦ or 160.5(3)◦ show considerably larger deviations from ideality than the angles C11–Ru1–O2 and C12–Ru2–O4 of 172.2(4)◦ and 168.9(4)◦ involving the C atoms of the carbonyl ligands. These differences, however, do not seem to be imposed by conformational constraints of macrocycle formation, since very similar observations were also made for similar mono- and diruthenium complexes with terminal benzoate ligands, e.g., Ru–O = 2.305(2) Å and 2.200(2) Å, O–Ru–Cst = 157.83(10)◦ , O–Ru–CCO = 170.39(11)◦ for the closely related complex Ru(CO)(Pi Pr3 )2 (CH=CH–C6 H5 )(κO,O0 -OOCC6 H4 -4SC(=O)CH3 ) [11]. The macrocycles therefore seem to be largely devoid of ring strain. This is also indicated by an only minute twisting of the P–Ru vectors, as indicated by torsional angles P–Ru···Ru–P of 0.2◦ or 3.0◦ along the divinylphenylene, and of 4.8◦ along the isophthalate linkers. The phenylene rings at the divinylphenylene linkers are rotated by 27.9◦ and 26.4◦ out of the coordination planes defined by the Ru atoms and the equatorial ligands. As was found for other tetraruthenium macrocycles of the same general architecture, the vinyl linkers at the Ru atoms are rotated outward from the interior cavity [2,4]. This conformation generates the most regular cavity shape, and was also found to be the most stable one by quantum chemical calculations [1]. Cavity dimensions in 4 are 12.7 Å × 8.3 Å as measured between opposite hydrogen atoms, which is very similar to the values obtained for other structurally characterized tetraruthenium macrocycles with isophthalate linkers [2]. Together with the rotation of the phenyl rings, the outward rotation at the phenylene linkers generates the necessary space within the central cavity to incorporate one benzene solvate molecule. The redox properties of macrocycles 1–4 were explored by cyclic and square wave voltammetric measurements in 0.1 M NBu4 PF6 /CH2 Cl2 solutions and, in the case of 1 and 4, also in the NBu4 + B{C6 H3 (CF3 )2 -3,5}4 − supporting electrolyte. Table 1 summarizes the relevant data from electrochemical experiments on the present complexes 1–4 and compares them to those for the dinuclear chloro-substituted precursor (Pi Pr3 )2 Cl(CO)Ru–CH=CH–C6 H4 –CH=CH–Ru(CO)Cl(Pi Pr3 )2 (Ru2 Cl2 ) [1] and its bis(benzoato) derivative (PhCOO-κO,O0 )(Pi Pr3 )2 (CO)Ru–CH=CH–C6 H4 –CH=CH–Ru(CO)(Pi Pr3 )2 –(κO,O0 -OOCPh) (Ru2 bza2 [11]; for their structures see Figure 5). All macrocycles are oxidized in two consecutive redox processes with potential splittings of 195 mV to 248 mV. Figure 6 shows a representative voltammogram of macrocycle 3; those of the other complexes can be found as Figures S30 to S34 of the Supplementary Materials. Each of these processes involves two electrons in total and corresponds to the stepwise loss of one electron from every conjugated divinylphenylene diruthenium side. Some small splitting ∆E1/2 between the individual one-electron waves is evident for the first composite redox process constituted by the 0/+ and +/2+ redox couples, in particular in square wave experiments. The latter also made it possible to derive individual half-wave potentials E1/2 for the individual processes by digital simulation of the overall peak shape (see Figures S35 to S40 of the Supplementary Materials). No such splitting is, however, seen for the second composite wave, corresponding to the overall 2+/4+ redox event. All oxidations involve the π-conjugated Ru–CH=CH–C6 H4 –CH=CH–Ru sides, which are largely identical for every macrocycle and only vary by the substituents at the isophthalate linker. Since the isophthalate linkers essentially act as insulators between the conjugated sides, they only exert an inductive influence. This also explains that variations of E1/2 values for equivalent redox processes between the individual macrocycles are rather small. Changing the anion of the supporting electrolyte from PF6 − to the even more weakly ion pairing B{C6 H3 (CF3 )2 -3,5}4 − anion leaves the splitting between the first and second one-electron steps unaltered (Table 1), while increasing the half-wave potential differences between the second and third oxidations (i.e., for the second charging of a conjugated side) by ca. 100 mV. Some further minor splitting between the 2+/3+ and the 3+/4+ waves is indicated by a broadening of the corresponding CV wave (see Figures S31 and S34 of the Supplementary Materials) and the square wave peaks. Digital simulation of the square wave voltammograms now required four separate peaks (Figures


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S36 and S40 of the Supplementary Materials), and the corresponding potentials are also provided in Table 1. It becomes evident that increasing the electron count at the ruthenium atoms from 16 to 18 does not only influence the energies also Inorganics 2018, 6, x FOR PEER REVIEW of the υ(CO) stretching vibrations of the carbonyl ligands but7 of 21 shifts the redox potentials cathodically by ca. 150 to 180 mV for the first, and by 90 to 130 mV for the second oxidation of an individual {Ru}–CH=CH–C6 H4 –CH=CH–{Ru} entity. Inorganics 2018, 6, x FOR PEER REVIEW 7 of 21

Figure 5. The diruthenium reference complexes Ru2Cl2 and Ru2bza2.

Table 1. Electrochemistry data for macrocycles 1–4 and the diruthenium analogs Ru 2bza2 and Ru2Cl2 1. Figure 5. The diruthenium reference complexes Ru Cl2 and Ru 2bza2. Figure 5. The diruthenium reference complexes Ru22Cl 2 and Ru2 bza2 .

Complex E1/20/+ (mV) E1/21+/2+ (mV) E1/2+2/4+ (mV) ΔE1/2+1/2+ (mV) ΔE1/22+/4+ (mV)

Table 1. Electrochemistry data for macrocycles 1–4 and the diruthenium analogs Ru 2bza2 and Ru2Cl2 11. 2 Table 1.1 Electrochemistry 1–4 and82 the diruthenium analogs Ru2 bza2 and −244 data for macrocycles −147 97 229 Ru2 Cl2 . 4 +2/4+ (mV) 1 3 −330 −241 89 (mV) ΔE1/22+/4+ 315 Complex E1/20/+ (mV) E1/21+/2+ (mV) E1/274/125 ΔE1/2+1/2+ (mV) +2/4+ (mV) +1/2+ (mV) 2+/4+ E1/2 0/+ −256 (mV) E1/2 1+/2+ (mV) E ∆E ∆E 1/2 1/2 1/2 −173 59 83 232 (mV) 1 −244 −147 82 97 229 −244 −147 8273 4 97 229 1 2 1 3 3 2 −256 −175 81 248 −330 −241 74/125 89 315 −330 −241 89 315 13 74/125 4 2 2 4 −220 −150 45 70 195 −256 −173 83 232 −256 −173 5959 83 232 2 2 2 4 4 2 3 −330 −255 57/114 75 312 −256 −175 81 248 −256 −175 7373 81 248 3 2 3 2 5 −220 − 150 45 70 195 4Ru4 2 2 2bza −250 ‐ 20 ‐ 270 −220 −150 45 70 195 −330 −255 75 312 4 3 3 57/114 45 4 Ru2Cl2 −75 ‐ 175 ‐ 250 −330 −255 57/114 75 312 Ru2 bza4 −250 270 20 5 2 1 In CH2Cl2 at r.t. and v = 100 mV/s or at a step width of 2 mV and a square wave frequency of 20 Hz −250 20 5 5 270 RuRu −75 - ‐ -‐ 250 175 2 Cl22bza2 5 1in square wave voltammetry. Potentials are provided against the ferrocene/ferrocenium redox scale. Ru 2Cl 2 r.t. and v−75 ‐ frequency of 20250 In CH = 100 mV/s or at ‐ a step width of 175 2 mV and a square wave Hz in square 2 Cl 2 at

Complex 2 2 2

2 With 0.1 M NBu + − 2 With 0.1 M NBu 3 With 0.02 M NBu wave voltammetry. Potentials are provided against the ferrocene/ferrocenium redox scale. 4+PF6− as the supporting electrolyte. 4+B{C6H 3(CF3)2‐3,5}4− as the 1 In CH 4 PF6 2Cl2 at r.t. and v = 100 mV/s or at a step width of 2 mV and a square wave frequency of 20 Hz 3 With 0.02 M NBu + B{C H (CF ) -3,5} − as the supporting electrolyte. 4 Separate as the supporting electrolyte. 4 6 3 3 2 4 4 5 supporting electrolyte. Separate potentials for the 2+/3+ and the 3+/4+ waves. Half‐wave potential in square wave voltammetry. Potentials are provided against the ferrocene/ferrocenium redox scale. potentials for the 2+/3+ and the 3+/4+ waves. 5 Half-wave potential for the +/2+ wave, which phenomenologically for the +/2+ wave, which phenomenologically corresponds to the 2+/3+ wave of a macrocyclic analog. 2corresponds 3 + − + to the 2+/3+ of a macrocyclic analog. With 0.1 M NBu 4 PF6 wave as the supporting electrolyte. With 0.02 M NBu4 B{C6H3(CF3)2‐3,5}4− as the

supporting electrolyte. 4 Separate potentials for the 2+/3+ and the 3+/4+ waves. 5 Half‐wave potential for the +/2+ wave, which phenomenologically corresponds to the 2+/3+ wave of a macrocyclic analog.

2Cl2, NBu +PF − , 0.1 M, at v = 100 mV/s, r.t. Figure 6. 6. Cyclic Cyclic voltammogram voltammogram of of macrocycle macrocycle 33 (CH (CHCl Figure 2 2 , NBu4 PF6 , 0.1 M, at v = 100 mV/s, r.t. 2Cl2 and Ru2bza2. diruthenium reference complexes Ru diruthenium reference complexes Ru2 Cl2 and Ru2 bza2. Figure 6. Cyclic voltammogram of macrocycle 3 (CH2Cl2, NBu4+PF6−, 0.1 M, at v = 100 mV/s, r.t. Previous studies on similar 2 + 2 tetraruthenium macrocycles assembled from divinylphenylene 2Cl2 and Ru2bza2. diruthenium reference complexes Ru Previous studies on similar 2 + 2 tetraruthenium macrocycles assembled from divinylphenylene 4+

6−

and isophthalate building blocks had indicated that the small splitting of the 0/+ and +/2+ redox and isophthalate building blocks had indicated that the small splitting of the 0/+ and +/2+ redox couples, which correspond to the stepwise charging of first the one and then the other Previous studies on similar 2 + 2 tetraruthenium macrocycles assembled from divinylphenylene couples, which correspond to the stepwise charging of first the one and then the other divinylphenylene divinylphenylene diruthenium sides of a macrocycle, are entirely due to electrostatic and inductive and isophthalate building blocks had indicated that the small splitting of the 0/+ and +/2+ redox diruthenium sides of a macrocycle, are entirely due to electrostatic and inductive effects, with no effects, with no indication for through‐space or through‐bond electronic interactions between them. couples, which correspond to the stepwise charging of first the one and then the other This also holds here, as is indicated by the results of our IR and UV/Vis/NIR spectroelectrochemical divinylphenylene diruthenium sides of a macrocycle, are entirely due to electrostatic and inductive experiments. Figure 7 provides a graphical account of the spectroscopic changes for the Ru(CO) effects, with no indication for through‐space or through‐bond electronic interactions between them. stretching vibrations and in the near infrared (NIR) for macrocycle 1; the results for the other This also holds here, as is indicated by the results of our IR and UV/Vis/NIR spectroelectrochemical macrocycles are included as Figures S41 to S52 in the Supplementary Materials. The corresponding experiments. Figure 7 provides a graphical account of the spectroscopic changes for the Ru(CO) data are summarized in Table 2. stretching vibrations and in the near infrared (NIR) for macrocycle 1; the results for the other


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indication for through-space or through-bond electronic interactions between them. This also holds here, as is indicated by the results of our IR and UV/Vis/NIR spectroelectrochemical experiments. Figure 7 provides a graphical account of the spectroscopic changes for the Ru(CO) stretching vibrations and in the near infrared (NIR) for macrocycle 1; the results for the other macrocycles are included as Inorganics 2018, 6, x FOR PEER REVIEW 8 of 21 Figures S41 to S52 in the Supplementary Materials. The corresponding data are summarized in Table 2.

Figure 7. Spectroscopic changes of the Ru(CO) bands (left) and in the near infrared (right) during the Figure 7. Spectroscopic changes of the Ru(CO) bands (left) and in the near infrared (right) during the 2+ to the tetracation oxidation of the neutral macrocycle 1 to its dication 1 oxidation of the neutral macrocycle 1 to its dication 12+2+ (top) and from dication 1 (top) and from dication 12+ to the tetracation 4+ + − + 6 , at r.t. − 4Cl2/0.1 M NBu4 PF 1 (bottom) in 1,2‐C 14+ (bottom) in 1,2-C2 H2H 4 Cl2 /0.1 M NBu4 PF6 , at r.t. Table 2. Energies of the υ(CO) stretches and UV/Vis/NIR data for macrocycles 1–4 and the analogous

Table 2. Energies of the υ(CO) stretches and UV/Vis/NIR data1,2for macrocycles 1–4 and the analogous diruthenium complex Ru2bza2 in their various oxidation states . diruthenium complex Ru2 bza2 in their various oxidation states 1,2 . Complex υ(CO) 1 λmax(εmax) 1 1 1 1901 354(85,000) Complex υ(CO) λmax (εmax ) 1 1927, 279(59,300), 492(35,700), 534(69,000), 587(83,000), 963(15,900), 1089(62,700), 1 12+ 1901 354(85,000) 1944 1259(95,000) 1927, 1944 279(59,300), 492(35,700), 534(69,000), 587(83,000), 963(15,900), 1089(62,700), 1259(95,000) 12+ 4+ 1 1973 279(79,200), 602(126,000) 1973 279(79,200), 602(126,000) 14+ 2 1901 354(85,000) 2 1901 354(85,000) 1927, 279(59,500), 495(37,000), 535(69,000), 587(83,000), 963(15,600), 1088(62,700), 2+ 1927, 1943 279(59,500), 495(37,000), 535(69,000), 587(83,000), 963(15,600), 1088(62,700), 1257(95,000) 2 22+ 1943 1257(95,000) 1973 279(79,600), 602(127,000) 24+ 1973 279(79,600), 602(127,000) 3 24+ 1902 354(70,700) 1902 354(70,700) 1928, 1944 283(63,300), (495(25,900), 535(48,600), 587(61,600) 936(13,400), 1085(46,900), 1256(72,000) 32+ 3 1972 282(65,300), 608 (102,000) 34+ 2+ 1928, 283(63,300), (495(25,900), 535(48,600), 587(61,600) 936(13,400), 1085(46,900), 3 4 1901 356(60,600) 1944 1256(72,000) 2+ 1928, 1944 279(46,400), 537(49,700), 589(61,000), 963(12,100), 1086(45,100), 1258(70,000) 4 34+ 1972 282(65,300), 608 (102,000) 1973 283(116,000), 364(42,700), 592(109,000) 44+ 4 1901 356(60,600) Ru2 bza2 1904 362(19,000) 1928, 279(46,400), 537(49,700), 589(61,000), 963(12,100), 1086(45,100), 1258(70,000) Ru2 bza24+2+ 1924, 1944 357(19300), 487(6600), 536(6800), 587(8000), 1016(9200), 1084(1900), 1272 (5800) 1944 1971 375 (9200), 427(9000), 606(13000) Ru2 bza2 2+4+ 4 1973 283(116,000), 364(42,700), 592(109,000) 1 υ(CO) in cm−1 ; λ ε in M−1 cm−1 ; in 1,2-C2 H4 Cl2 /0.1 M NBu4 + PF6 − . 2 Data for Ru2 bza2 n+ from ref. [11]. max in nm, Ru2bza2 1904 362(19,000) Ru2bza2+

1924, 357(19300), 487(6600), 536(6800), 587(8000), 1016(9200), 1084(1900), 1272 (5800) 1944 oxidation of the macrocycles to their dications, we observe the expected 1971 375 (9200), 427(9000), 606(13000)

On gradual blue shift Ru2bza22+ of the Ru(CO) bands and the formation of a pattern of a weaker band at a higher energy of 1944 1 υ(CO) in cm−1; λmax in nm, ε in M−1 cm−1; in 1,2‐C2H4Cl2/0.1 M NBu4+PF6−. 2 Data for Ru2bza2n+ from −1 . This behavior is cm−1 and a more intense, main feature at a lower energy of 1927 or 1928 cm ref. [11].


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identical to that of linear divinylarylene-bridged diruthenium complexes [1,8,11,12]. The initially puzzling observation of two Ru(CO) bands (suggesting that the two Ru(CO) sites are electronically inequivalent) despite complete charge delocalization as indicated by detailed quantum chemical calculations and EPR studies was finally traced to the lifting of the degeneracy between the symmetric and antisymmetric combinations of the Ru(CO) stretches [1,35]. Oxidation to the dications is also accompanied by the growth of highly intense, structured and sharp NIR bands at ca. 10,500 cm−1 , 9200 cm−1 , and 8000 cm−1 (ca. 950 nm, 1085 nm and 1250 nm), with half-widths of the order of 800 cm−1 , 1100 cm−1 , and 1000–1430 cm−1 . These bands correspond to the electronic β-HOSO → β-LUSO excitation within the open-shell divinylphenylene–diruthenium chromophore(s). No clear distinction between the 0/+ and +/2+ processes was evident in any of these experiments. This is, however, due to the absence of any specific absorption band of the monocations of these macrocycles with one monooxidized and one neutral divinylphenylene diruthenium side, and not to an inherent failure of our optically transparent thin layer electrolysis (OTTLE) cell to resolve two close-lying one-electron processes. In this respect we note that similar experiments on the cis- and trans-isomers of bis(styryl)ethene-bridged diruthenium complexes {Ru}–CH=CH–C6 H4 –CH=CH–C6 H4 –CH=CH–{Ru} had clearly identified the intermediate radical cations despite similar or even smaller half-wave potential splittings (74 mV to 49 mV) than in the present cases [10]. Simple thermodynamic considerations indicate that half-wave potential splittings of 45 mV to 82 mV correspond to equilibrium constants Kc of 6 to 24 for the comproportionation reaction according to Equation (1), where MC represents an individual macrocycle molecule. MC2+ + MC 2 MC+

(1)

This in turn means that, after stoichiometric release of one electron per macrocycle (which point must be passed in every experiment), the composition of the solution varies between 55% of the monocation and 22.5% of each the dicationic and neutral forms (Kc = 6), and 71% of the monocation and 14.5% of each the dicationic and neutral forms (Kc = 24). Thus, in every instance, the radical cation must be formed and is even the dominant species at intermediate stages of the spectroelectrochemical experiment. The monocations thus contain no specific Ru(CO) and electronic NIR bands apart from those of the isolated divinylphenylene diruthenium chromophores in their respective oxidation states. Hence, the (hypothetical) spectra of the pure monocations would essentially be indistinguishable from those of a 1:1 mixture of the dicationic and the neutral macrocycles. This in turn indicates the absence of any electronic interaction through the isophthalate linkers (i.e., through bond) or through space. On close inspection, however, we note a gradual blue shift of the most intense and most red-shifted NIR band on continuous oxidation. This is likely due to a slight change of the electron-donating capabilities of the isophthalate linkers, which are bound to one oxidized and one reduced divinylphenylene diruthenium entity at initial stages of the electrolysis, but to two oxidized ones near the point of full conversion to the dications. The electronic properties of the coligands at ruthenium will affect the energies of the frontier molecular orbitals β-HOSO and β-LUSO that are involved in the corresponding electronic transition and their energy differences, which explains the slight positional changes from the initial to the later stages of the IR/NIR spectroelectrochemical experiment. These changes in inductive effects relate to the contribution of the ∆Gind term to the free enthalpy change associated with two consecutive redox processes and will therefore also contribute to the observed half-wave potential splittings [36–40]. Oxidation of the dications to the tetracations is accompanied by a further blue shift of the Ru(CO) bands along with an intensity decrease. This is particularly true for the symmetric combination of the individual Ru(CO) stretches, such that only one Ru(CO) band remains. Likewise, the NIR absorptions of the open-shell divinylphenylene diruthenium chromophores bleach completely (see Figure 7 and Figures S44, S48 and S52 of the Supplementary Materials). Again, the intermittently formed trications have no specific spectroscopic signatures that would distinguish them from the


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10 of 21

dications (the remaining singly oxidized divinylphenylene diruthenium side) or the tetracations (the remaining singly oxidized divinylphenylene side) or the tetracations (the doubly doubly oxidized divinylphenylene dirutheniumdiruthenium side). oxidized divinylphenylene diruthenium side). Changes in the electronic spectra of the macrocycles are exemplified for complex 3 in Figure 8. Changes in the electronic spectra of the macrocycles are exemplified for complex 3 in Figure 8. Representative spectra for all other macrocycles are displayed in Figures S53 to10 of 21 S58 of the Inorganics 2018, 6, x FOR PEER REVIEW Representative spectra for all other macrocycles are displayed in Figures S53 to S58 of the Supplementary Materials while pertinent data are collected in Table 2. Visual impressions of 200 Supplementary Materials while pertinent data are collected in Table 2. Visual impressions of 200 μM remaining singly oxidized divinylphenylene diruthenium side) or the tetracations (the doubly µM solutions of macrocycle 1 in its neutral, dicationic and tetracationic states are displayed in Figure 9. solutions of macrocycle 1 in its neutral, dicationic and tetracationic states are displayed in Figure 9. oxidized divinylphenylene diruthenium side). On stepwise oxidation, the faint yellow hue of the neutral macrocycles gives way to a deep purple Changes in the electronic spectra of the macrocycles are exemplified for complex 3 in Figure 8. On stepwise oxidation, the faint yellow hue of the neutral macrocycles gives way to a deep purple coloration ofRepresentative the dications. The latter due macrocycles to structured cover the range spectra for all isother are prominent displayed in absorptions Figures S53 that to S58 of the coloration of the dications. The latter is due to structured prominent absorptions that cover the range 1 ·cm −1 . Concomitantly, the equally Supplementary Materials while pertinent data are collected in Table 2. Visual impressions of 200 μM −1. Concomitantly, the equally of 500–600 nm with extinction coefficients larger than 6 × 1044 M M−1−∙cm of 500–600 nm with extinction coefficients larger than 6 × 10 solutions of macrocycle 1 in its neutral, dicationic and tetracationic states are displayed in Figure 9. intense NIR features that were already observed in the IR/NIR experiments appear. Both kinds of intense NIR features that were already observed in the IR/NIR experiments appear. Both kinds On stepwise oxidation, the faint yellow hue of the neutral macrocycles gives way to a deep purple absorptions can can be be described within the the conjugated metal–organic of absorptions describedas asπ π→ →π* π*type typetransitions transitions within conjugated metal–organic coloration of the dications. The latter is due to structured prominent absorptions that cover the range chromophores [1,4]. On further oxidation to the associated tetracations, the colour changes to deep 4 M−1∙cm−1. Concomitantly, the equally chromophores [1,4]. On further oxidation to the associated tetracations, the colour changes to deep of 500–600 nm with extinction coefficients larger than 6 × 10 intense NIR features that were already observed in the IR/NIR experiments appear. Both kinds of royalroyal blue or blue‐green. Electronic spectra indicate a red shift and broadening of the prominent Vis blue or blue-green. Electronic spectra indicate a red shift and broadening of the prominent absorptions together with a loss of the fine structure of the absorption bands and a further gain in absorptions can be described as π → π* type transitions within the conjugated metal–organic Vis absorptions together with a loss of the fine structure of the absorption bands and a further gain −1∙cm−1. In line with our chromophores [1,4]. On further oxidation to the associated tetracations, the colour changes to deep absorptivity to ultimately reach extinction coefficients of >1 × 105 M 5 M−1 ·cm−1 . In line with our in absorptivity to ultimately reach extinction coefficients of >1 × 10 royal blue or blue‐green. Electronic spectra indicate a red shift and broadening of the prominent Vis observations from the IR/NIR experiments, oxidation of the di‐ to the tetracations is accompanied by observations from the IR/NIR experiments, oxidation of the di- to the tetracations is accompanied by absorptions together with a loss of the fine structure of the absorption bands and a further gain in a complete bleach of the NIR bands. absorptivity to NIR ultimately reach extinction coefficients of >1 × 105 M−1∙cm−1. In line with our a complete bleach of the bands. observations from the IR/NIR experiments, oxidation of the di‐ to the tetracations is accompanied by a complete bleach of the NIR bands.

Figure 8. Changes in the UV/Vis/NIR spectra on oxidation of neutral macrocycle 3 to the dicationic Figure 8. Changes in the UV/Vis/NIR spectra on oxidation of neutral macrocycle 3 to the dicationic Figure 8. Changes in the UV/Vis/NIR spectra on oxidation of neutral macrocycle 3 to the dicationic 2+ 4+ + − 2+ (left) and from the di‐ to the tetracationic state 3 statestate 3 3 (left) and2+ from the di- to the tetracationic state4+3 (right, 1,2‐C (right, 1,2-C NBu 2H4Cl 2, NBu 6−, r.t.). 2H 4 Cl24,++PF 4 PF6 , r.t.). 4+ − state 3 (left) and from the di‐ to the tetracationic state 3 (right, 1,2‐C2H4Cl2, NBu4 PF6 , r.t.).

Figure 9. Visual impressions of the neutral (left), dicationic (middle) and tetracationic (right) forms Visual impressions of the neutral (left), dicationic 2Cl(middle) 2 solution. and tetracationic (right) forms of macrocycle 1 at concentration levels of 200 μM in CH

Figure 9. Figure 9. Visual impressions of the neutral (left), dicationic (middle) and tetracationic (right) forms macrocycle 1 at concentration levels of 200 µM in CH2 Cl solution. 22 solution. 2Cl of macrocycle 1 at concentration levels of 200 μM in CH

of

While the electronic bands of the di‐ and tetracations of the present macrocycles are, in terms of their position and general appearance, very similar to those of the radical cations and dications of

While the electronic bands of the di‐ and tetracations of the present macrocycles are, in terms of While the electronic bands of the di- and tetracations of the present macrocycles are, in terms of their position and general appearance, very similar to those of the radical cations and dications of their position and general appearance, very similar to those of the radical cations and dications of

analogous divinylphenylene-bridged diruthenium complexes like Ru2 Cl2 or Ru2 bza2 (see Figure 5), their extinction coefficients clearly surpass those of their open, linear analogues by a factor of >2


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analogous divinylphenylene‐bridged diruthenium complexes like Ru 2Cl2 or Ru2bza2 (see Figure 5), Inorganics 2018, 6, 73 11 of 21 their extinction coefficients clearly surpass those of their open, linear analogues by a factor of >2 (see Table 2; a value of 2 would be expected for the effect of simply doubling the number of the (see Table 2; a value of probably 2 would be expected for theconformational effect of simply doubling of chromophores). This is due to restricted freedom of the the number individual the chromophores). This is probably due to restricted conformational freedom of the individual chromophores once they are embedded into rigidified macrocyclic structures. Their linear chromophoresanalogues once they are into rigidified macrocyclic structures. Theirwith linearrespect diruthenium diruthenium can embedded exist as mixtures of cisoid and transoid conformers to the analogues can exist as mixtures of cisoid and transoid conformers with respect to the orientation of the orientation of the Ru–CO vectors and may also exhibit larger torsions around the bonds connecting Ru–CO vectors and may also exhibit larger torsions around the bonds connecting the vinyl groups the vinyl groups to the ruthenium atoms or the phenyl rings. These observations qualify the present to the rutheniummacrocycles atoms or the rings. powerful These observations qualify thedyes present tetraruthenium tetraruthenium as phenyl particularly polyelectrochromic for the Vis and the macrocycles as particularly powerful polyelectrochromic dyes for the Vis and the NIR. NIR. Samples of the di- and tetracations of macrocycles 1–4 for EPR investigations were prepared by Samples of the di‐ and tetracations of macrocycles 1–4 for EPR investigations were prepared by selective oxidation of the neutral precursors with ferrocenium (E selective oxidation of the neutral precursors with ferrocenium (E 1/2 = 0 mV) or acetylferrocenium (E 1/2 1/2 = 0 mV) or acetylferrocenium (E = 270 mV) hexafluorophosphate in CH Cl solution [41]. Both kinds of species are EPR active = 270 mV) hexafluorophosphate in CH 2Cl2 solution [41]. Both kinds of species are EPR active and 2 2 1/2 and provide broadened isotropic signals with no resolved hyperfine splittings in fluid solution at provide broadened isotropic signals with no resolved hyperfine splittings in fluid solution at r.t. and r.t. and in frozen solutions. g values are close to 2.02 for the dications and slightly higher, ca. in frozen solutions. g values are close to 2.02 for the dications and slightly higher, ca. 2.03, for the 2.03, for the tetracations (see Table 3). We also note that, for similar concentration levels, signal tetracations (see Table 3). We also note that, for similar concentration levels, signal intensities of the intensities of the tetracations are appreciably smaller than those for the dications. Figure 10 displays tetracations are appreciably smaller than those for the dications. Figure 10 displays representative 2+ and 3 4+ at r.t.; additional spectra at T = 123 K and those for the other complexes can representative EPR spectra of 32+ and 34+ at r.t.; additional spectra at T = 123 K and those for the EPR spectra of 3 other complexes can be found as Figures S59 to S70 of the Supplementary Materials. In no case be found as Figures S59 to S70 of the Supplementary Materials. In no case could a half‐field signal could a half-field signal corresponding to a ∆ms ± 2 transition be observed. This indicates that s ± 2 transition be observed. This indicates that (i) every individual spin of the corresponding to a ∆m (i) every individual spin of the dications is delocalized over one divinylphenylene diruthenium dications is delocalized over one divinylphenylene diruthenium side with major contributions of the side with major contributions of the π-conjugated organic linker and does not interact with the π‐conjugated organic linker and does not interact with the other over the isophthalate linkers to a other over the isophthalate linkers to a detectable extent; and (ii) the two spins at an individual detectable extent; and (ii) the two spins at an individual divinylphenylene diruthenium side in the divinylphenylene diruthenium side in the tetracationic state also act independently from each other tetracationic state also act independently from each other and do not couple antiferromagnetically, and do notthe couple antiferromagnetically, although the para-phenylene linkage normally although para‐phenylene linkage normally supports such coupling [42–46]. This supports kind of such coupling This kindfor of behaviour wasof also the dication of thecomplex similar behaviour was [42–46]. also observed the dication the observed similar for linear diruthenium i i i i linear complex (P 2Pr Pr3 )2 and studied in (P Pr3)2diruthenium Cl(CO)Ru–C6H 2(2,5‐OBu) –Ru(CO)Cl(P Pr3)26 H and studied 2 –Ru(CO)Cl(P in detail by variable‐temperature 3 )2 Cl(CO)Ru–C 2 (2,5-OBu) detailspectroscopy by variable-temperature EPR to 4 K [1]. Particularly well examples represented EPR down to 4 K [1]. spectroscopy Particularly down well represented among the few of among the few examples of paramagnetic compounds with two spin centers interconnected by paramagnetic compounds with two spin centers interconnected by para‐phenylene linkers are those para-phenylene linkers are those with two Ar2 N•+centers -aminiumyl-type paramagnetic centers interlinked with two Ar2N•+ ‐aminiumyl‐type paramagnetic interlinked by long π‐conjugated spacers by long π-conjugatedmotifs spacers with para-phenylene motifsdicationic [47–49]. Quite interestingly, dicationic with para‐phenylene [47–49]. Quite interestingly, complexes [(PiPr3)2Cl(CO)Ru– i Pr )2+Cl(CO)Ru–C H –N(C H R-4) ]2+ (R = CHO, COCH , COOMe, Me, OMe), complexes [(P C 6H4–N(C6H 4R‐4) 23] 2 (R = CHO, COCH 3, COOMe, both motifs in one 6 4 6 4 2 Me, OMe), which combine 3 which combine both motifs in one compound, show the same kind of behaviour [50]. Common compound, show the same kind of behaviour [50]. Common to all these systems is that the ability of to all these systems is that the ability of the terminal entities to accommodate the unpaired spin density the terminal entities to accommodate the unpaired spin density allows the arylene linkers to retain allows the arylene linkers to retain their aromatic Clar’s sextets rather than sacrificing them in favour their aromatic Clar’s sextets rather than sacrificing them in favour of quinoidal structures. The latter of quinoidal structures. The latter are necessary prerequisites for achieving antiferromagnetic coupling are necessary prerequisites for achieving antiferromagnetic coupling (see Figure 11). In the absence (see Figure 11). In the absence of appreciable magnetic interactions between the terminal spin-bearing of appreciable magnetic interactions between the terminal spin‐bearing sites the paramagnetic triplet sites the paramagnetic triplet and the diamagnetic singlet diradical structures will coexist in solution. and the diamagnetic singlet diradical structures will coexist in solution.

Figure 10. EPR spectra of the di‐ (left) and tetracation (right) of macrocycle 3 (CH2Cl2, r.t.). Figure 10. EPR spectra of the di- (left) and tetracation (right) of macrocycle 3 (CH2 Cl2 , r.t.).


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Table 3. g values for oxidized complexes 1–4 in CH2 Cl2 . Table 3. g values for oxidized complexes 1–4 in CH2Cl2. Complex Complex 1 2 3 4

1 2 3 4

Dication Dication r.t. r.t.

123 K 123 K

2.019 2.019 2.019 2.019 2.019 2.019 2.019 2.019

2.019 2.019 2.018 2.018 2.018 2.018 2.018 2.018

Tetracation Tetracation r.t. r.t. 123 K 123 K 2.030 2.036 2.030 2.036 2.031 2.031 2.028 2.028 2.031 2.028 2.028 2.031 2.032 2.032 2.029 2.029

Figure 11. Possible structures and spin multiplicities for compounds with two paramagnetic redox Figure 11. Possible structures and spin multiplicities for compounds with two paramagnetic redox • centers RC centers RC• bridged by a para‐phenylene spacer. bridged by a para-phenylene spacer.

Initial attempts to utilize functionalized macrocycles 1–4 in a complexes‐as‐ligands approach Initial attempts to utilize functionalized macrocycles 1–4 in a complexes-as-ligands approach [51,52] [51,52] for further metal coordination were frustrated by their rather poor solubilities and their for further metal coordination were frustrated by their rather poor solubilities and their sensitivity sensitivity towards even mildly Lewis‐acidic and oxophilic cations like Zn2+ or Cu2+. Thus, addition towards even mildly Lewis-acidic and oxophilic cations like Zn2+ or Cu2+ . Thus, addition of zinc(II) or of zinc(II) or copper(II) salts to complexes 1 and 2 led to rapid decomposition as indicated by a colour copper(II) salts to complexes 1 and 2 led to rapid decomposition as indicated by a colour change to change to brown, the deposition of brownish solids, and the loss of the Ru(CO) stretches in the brown, the deposition of brownish solids, and the loss of the Ru(CO) stretches in the solution phase solution phase and these solid deposits. We assume that these cations compete with the Ru centers and these solid deposits. We assume that these cations compete with the Ru centers for the carboxylate for the carboxylate linkers, which may ultimately lead to the opening of the macrocycles. Further linkers, which may ultimately lead to the opening of the macrocycles. Further attempts to engage attempts to engage macrocycle 2 in typical cyclometalation reactions, e.g., with PtCl2(dmso)2, were macrocycle 2 in typical cyclometalation reactions, e.g., with PtCl2 (dmso)2 , were thwarted by their thwarted by their insufficient thermal stability to withstand the typical reaction conditions that are insufficient thermal stability to withstand the typical reaction conditions that are required to induce required to induce ligand substitution of such Pt complexes. Structural models of macrocycle 1 also ligand substitution of such Pt complexes. Structural models of macrocycle 1 also indicate that the outer indicate that the outer pyridyl rings may be spatially too close to the isophthalate carboxylate pyridyl rings may be spatially too close to the isophthalate carboxylate functionalities to allow for the functionalities to allow for the proper orientation for providing a tridentate binding pocket. We note, proper orientation for providing a tridentate binding pocket. We note, however, that macrocycle 4, however, that macrocycle 4, due to its easily deprotected Au‐binding thiolate functions, has the due to its easily deprotected Au-binding thiolate functions, has the potential to bridge Au nanogap potential to bridge Au nanogap electrodes for measuring molecular conductivities in an STM‐based electrodes for measuring molecular conductivities in an STM-based setup. Work along these lines is setup. Work along these lines is presently being pursued, and the results will be reported on a presently being pursued, and the results will be reported on a separate occasion. separate occasion. 3. Materials, Methods, Syntheses and Characterization Data 3. Materials, Methods, Syntheses and Characterization Data 3.1. Materials and General Methods 3.1. Materials and General Methods All manipulations were carried out under a nitrogen atmosphere. Solvents were dried and All prior manipulations carried under a nitrogen atmosphere. Solvents were dried and distilled to use. Allwere reagents fromout commercial sources were used without further purification. 1distilled prior to use. All reagents from commercial sources were used without further purification. 13 1 31 1 H NMR (400 MHz), C{ H} NMR (101 MHz) and P{ H}-NMR (162 MHz) spectra were measured 1H NMR (400 MHz), 13C{1H} NMR (101 MHz) and 31P{1H}‐NMR (162 MHz) spectra were measured on a Bruker AvanceIII 400 spectrometer (Bruker, Billerica, MA, USA), and 1 H-NMR (600 MHz) 1H‐NMR (600 MHz) and on a Bruker AvanceIII 400 spectrometer (Bruker, Billerica, MA, USA), and and 13 C{1 H} NMR (151 MHz) spectra on a Bruker AvanceIII 600 spectrometer (Bruker, Billerica, 13C{1H} NMR (151 MHz) spectra on a Bruker AvanceIII 600 spectrometer (Bruker, Billerica, MA, USA). MA, USA). {Ru(CO)Cl(Pi Pr3 )2 }2 (1,4-(CH=CH)2 –C6 H4 ) [8], 30 ,50 -dimethyl-2,20 :60 ,200 -terpyridine [22] iPr3)2}2(1,4‐(CH=CH)2–C6H4) [8], 3′,5′‐dimethyl‐2,2′:6′,2′′‐terpyridine [22] and 5‐ {Ru(CO)Cl(P and 5-mercaptoisophthalic acid [24] were prepared according to literature methods. ESI-MS data mercaptoisophthalic acid [24] were prepared to literature data from was was acquired on a Bruker micrOTOF II massaccording spectrometer (Bruker, methods. Billerica, ESI‐MS MA, USA) + − acquired on a Bruker micrOTOF II mass spectrometer (Bruker, Billerica, MA, USA) from partially partially oxidized analyte/CHCl3 solutions employing [Cp2 Fe] PF6 as the oxidant. Combustion oxidized analyte/CHCl solutions employing [Cp 2Fe]+PF6− as the oxidant. Combustion analysis was analysis was conducted 3with an Elementar vario MICRO cube CHN-analyzer from Heraeus (Heraeus, conducted with an Elementar vario MICRO cube CHN‐analyzer from Heraeus (Heraeus, Hanau, Hanau, Germany). Germany). X-ray diffraction analysis of a single crystal of macrocycle 4 was performed at 100 K on a STOE X‐ray diffraction analysis of a single crystal of macrocycle 4 was performed at 100 K on a STOE IPDS-II diffractometer (STOE, Darmstadt, Germany) equipped with a graphite-monochromated IPDS‐II diffractometer (STOE, Darmstadt, Germany) equipped with a graphite‐monochromated radiation source (λ = 0.71073 Å) and an image plate detection system. A crystal mounted on a fine


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radiation source (λ = 0.71073 Å) and an image plate detection system. A crystal mounted on a fine glass fiber with silicon grease was employed. If not indicated otherwise, the selection, integration, and averaging procedure of the measured reflection intensities, the determination of the unit cell dimensions and a least-squares fit of the 2θ values as well as data reduction, LP-correction and space group determination were performed using the X-Area software package delivered with the diffractometer. A semiempirical absorption correction was performed [53]. All structures were solved by the heavy-atom methods (SHELXS-97, [54] SHELXS-2014, [55] and OLEX2 [56]). Structure solutions were completed with difference Fourier syntheses and full-matrix last-squares refinements using SHELXL-97, [54] SHELXS-2014, [55] and OLEX2 [56] minimizing ω(Fo 2 − Fc 2 )2 . The weighted R factor (wR2 ) and the goodness of fit GOF are based on F2 . All non-hydrogen atoms were refined with anisotropic displacement parameters, while hydrogen atoms were treated in a riding model. Molecular structures in this work are plotted with the Mercury program [57]. The crystallographic data file for macrocycle 4 has been deposited at the Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ, [Fax: + 44 1223/336-033; E-mail [email protected].] under the deposition number CCDC 1846386 and can be obtained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html. 3.2. Electrochemical and Spectroelectrochemical Measurements All electrochemical experiments were performed in a home-built cylindrical vacuum-tight one-compartment cell equipped with a spiral-shaped Pt-wire and an Ag-wire as the counter and reference electrodes. The electrodes are sealed into glass capillaries that connect via Quickfit screws at opposite sides of the cell. A platinum electrode is used as the working electrode and is attached from the top port via a Teflon screw cap with a suitable fitting. Before measurements, the working electrode was polished with 1 µm and then 0.25 µm diamond pastes (Buehler-Wirtz, Lake Bluff, IL, USA). Measurements were carried out in argon-saturated solutions containing CH2 Cl2 and n Bu4N+ PF6 − or n Bu4N+ B{C6 H3 (CF3 )2 -3,5}4 − as the supporting electrolyte. Referencing was done with addition of cobaltocenium hexafluorophosphate as an internal standard. Representative sets of scans were repeated with the added standard. The final referencing was done against the ferrocene/ferrocenium (Cp2 Fe0/+ ) redox couple with E1/2 (Cp2 Co+/0 ) = −1330 mV vs. Cp2 Fe0/+ . Electrochemical data were acquired BASi potentiostat (Bioanalytical Systems, West Lafayette, IN, USA). The OTTLE cell was home-built and comprises of a Pt-mesh working and counter electrode and a thin Ag/AgCl wire as a pseudoreference electrode sandwiched between the CaF2 windows of a conventional liquid IR cell. Its design is based on that of Hartl et al. [58]. The working electrode is positioned in the beam the spectrometer. For the spectroelectrochemical experiments a Wenking POS2 potentiostat (Bank Elektronik-Intelligent Controls GmbH, Pohlheim, Germany) was used. FT-IR spectra were recorded using a Bruker Tensor II FT-IR spectrometer (Bruker, Billerica, MA, USA). UV/Vis/NIR spectra were obtained on a TIDAS fiberoptic diode array spectrometer (combined MCS UV/NIR and PGS NIR instrumentation) from j&m Analytik AG, Essingen, Germany. EPR spectra were obtained using an X-Band tabletop spectrometer (MiniScope MS 400) build by Magnettech GmbH, Berlin, Germany. All measurements were performed at room temperature and at −150 ◦ C. Macrocycles were oxidized chemically employing ferrocenium hexafluorophosphate or acetylferrocenium hexafluoroantimonate.

Inorganics 2018, 6, x FOR PEER REVIEW Inorganics 2018, 6, 73 Inorganics 2018, 6, x FOR PEER REVIEW

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3.3. Syntheses and Characterization 3.3. Syntheses and Characterization 3.3. Syntheses and Characterization 3.3.1. Syntheses and Characterization of 2,6‐Di(pyrid‐2‐yl)‐pyridine‐3,5‐dicarboxylic acid dimethyl 3.3.1. Syntheses and Characterization of 2,6‐Di(pyrid‐2‐yl)‐pyridine‐3,5‐dicarboxylic acid dimethyl 3.3.1. Syntheses and Characterization of 2,6-Di(pyrid-2-yl)-pyridine-3,5-dicarboxylic acid dimethyl ester (IL1) ester (IL1) ester (IL1)

30 ,50 -Dimethyl-[2,20 ,60 ,200 ]terpyridine (738 mg, 2.83 mmol) and KMnO444 (2.23 g, 14.13 mmol) were (2.23 g, 14.13 mmol) were 3′,5′‐Dimethyl‐[2,2′,6′,2′′]terpyridine (738 mg, 2.83 mmol) and KMnO (2.23 g, 14.13 mmol) were 3′,5′‐Dimethyl‐[2,2′,6′,2′′]terpyridine (738 mg, 2.83 mmol) and KMnO suspended in 200 mL of water and heated to reflux for 24 h. Upon heating, the purple colour of suspended in 200 mL of water and heated to reflux for 24 h. Upon heating, the purple colour of the suspended in 200 mL of water and heated to reflux for 24 h. Upon heating, the purple colour of the the suspension slowly faded. Subsequent filtration and washing with 40 mL of water and 80 of suspension slowly faded. Subsequent filtration and washing with 40 mL of water and 80 of MeOH suspension slowly faded. Subsequent filtration and washing with 40 mL of water and 80 of MeOH MeOH followed by evaporation of the solvents gave the crude oxidized product. The solid was followed by evaporation of the solvents gave the crude oxidized product. The solid was dissolved in followed by evaporation of the solvents gave the crude oxidized product. The solid was dissolved in dissolved insulfuric methanolic acid (200 mL,and 4% heated vol.) and reflux for 24 h.cooling After cooling to methanolic sulfuric acid sulfuric (200 mL, mL, 4% vol.) and heated to heated reflux to for 24 h. h. After cooling to room room methanolic acid (200 4% vol.) to reflux for 24 After to room temperature, aqueous NaHCO was added until the pH of the solution reached 7. Subsequent 3 added temperature, aqueous aqueous NaHCO NaHCO33 was was added until until the the pH pH of of the the solution solution reached reached 7. 7. Subsequent Subsequent temperature, evaporation of the solvents and extraction of the residue with 140 mL of CHCl /water, separation and 3 evaporation of the solvents and extraction of the residue with 140 mL of CHCl 3 /water, separation and evaporation of the solvents and extraction of the residue with 140 mL of CHCl3/water, separation and drying of the organic phase over Na SO and solvent removal gave the crude product. Purification on 2 4 drying of the organic phase over Na22SO SO44 and solvent removal gave the crude product. Purification and solvent removal gave the crude product. Purification drying of the organic phase over Na silica gel (ethyl acetate:petroleum benzene 3:2) yielded a colorless powder. Yield 310 mg, 31%. on silica gel (ethyl acetate:petroleum benzene 3:2) yielded a colorless powder. Yield 310 mg, 31%. on silica gel (ethyl acetate:petroleum benzene 3:2) yielded a colorless powder. Yield 310 mg, 31%. 1 H NMR (400 MHz, CDCl ): δ (ppm) = 8.63 (ddd, 3 3J = 4.8 Hz, 444JJJHH = 1.8 Hz, 555JJJHH = 0.9 Hz, 2H, 11H NMR (400 MHz, CDCl H NMR (400 MHz, CDCl333): δ (ppm) = 8.63 (ddd, ): δ (ppm) = 8.63 (ddd, 3JJHH HH = 4.8 Hz, = 4.8 Hz, HH = 1.8 Hz, = 1.8 Hz, HH = 0.9 Hz, 2H, HH HH HH = 0.9 Hz, 2H, 3 4 5 3J H9), 8.29 (ddd, J = 7.9 Hz, J = 1.0, J = 0.9 Hz, H6), 8.23 (s, 1H, H3), 7.85 (td, 3 4 5 3 HH HH HH HH = 7.844JHz, 3JJHH H9), 8.29 (ddd, 3JJHH HH = 7.9 Hz, 4JJHH HH = 1.0, 5JJHH HH = 0.9 Hz, H6), 8.23 (s, 1H, H3), 7.85 (td, = 0.9 Hz, H6), 8.23 (s, 1H, H3), 7.85 (td, HH = 7.8 Hz, = 7.8 Hz, JHH HH H9), 8.29 (ddd, = 7.9 Hz, = 1.0, 4J 3 3 4 = 1.8 Hz, 2H, H7), 7.34 J = 7.8 Hz, J = 4.8 Hz, J = 1.0. Hz, 2H, H8), 3.82 3J(ddd, 3JHH 4JHH HH HH HH HH 3 3 4 = 1.8 Hz, 2H, H7), 7.34 (ddd, HH = 7.8 Hz, = 4.8 Hz, = 1.0. Hz, 2H, H8), 3.82 (s, 6H, H10). = 1.8 Hz, 2H, H7), 7.34 (ddd, JHH = 7.8 Hz, JHH = 4.8 Hz, JHH = 1.0. Hz, 2H, H8), 3.82 (s, 6H, H10). (s, 6H, H10). 13C{11H} NMR (100 MHz, CDCl ): δ (ppm) = 168.8 (s, C1), 155.6 (s, C4), 155.3 (s, C5), 148.7 (s, C9), 13 C{ H} NMR (100 MHz, CDCl33): δ (ppm) = 168.8 (s, C1), 155.6 (s, C4), 155.3 (s, C5), 148.7 (s, C9), 13 C{1 H} NMR (100 MHz, CDCl ): δ (ppm) = 168.8 (s, C1), 155.6 (s, C4), 155.3 (s, C5), 148.7 (s, C9), 3 138.4 (s, C3), 136.9 (s, C7), 127.4 (s, C2), 124.2 (s, C8), 123.2 (s, C6), 52.6 (s, C10). 138.4 (s, C3), 136.9 (s, C7), 127.4 (s, C2), 124.2 (s, C8), 123.2 (s, C6), 52.6 (s, C10). 138.4Elemental analysis (CHN):(C (s, C3), 136.9 (s, C7), 127.4 (s, C2), (s, C8), 123.2 (s, C6), 52.6 (s, C10). H1515124.2 N33O O44) Calc. (found): C, 65.32 (65.19); H, 4.33 (4.53); N, 12.03 ) Calc. (found): C, 65.32 (65.19); H, 4.33 (4.53); N, 12.03 Elemental analysis (CHN):(C1919H N Elemental analysis (CHN):(C H N O ) 19 15 3 4 Calc. (found): C, 65.32 (65.19); H, 4.33 (4.53); N, (12.03). (12.03). 12.03 (12.03).

3.3.2. Syntheses and Characterization of 3,5‐Bis(pyrid‐2‐yl)‐phenylethynyl isophthalic acid dimethyl 3.3.2. Syntheses and Characterization of 3,5‐Bis(pyrid‐2‐yl)‐phenylethynyl isophthalic acid dimethyl 3.3.2. Syntheses and Characterization of 3,5-Bis(pyrid-2-yl)-phenylethynyl isophthalic acid dimethyl ester (IL2) ester (IL2) ester (IL2)

1,3-Dimethyl-5-ethynyl-isophthalic acid (2.07 mmol), 1-bromo-3,5-bis(2-pyridinyl)-benzene (653, 1,3‐Dimethyl‐5‐ethynyl‐isophthalic acid (2.07 mmol), 1‐bromo‐3,5‐bis(2‐pyridinyl)‐benzene 1,3‐Dimethyl‐5‐ethynyl‐isophthalic acid (2.07 mmol), 1‐bromo‐3,5‐bis(2‐pyridinyl)‐benzene 2.10 mmol), Pd(PPh ) (97 mg, 4 mol.%) and CuI (16 mg, 4 mol.%) were dissolved in 90 mL of 3 4 3)4 (97 mg, 4 mol.%) and CuI (16 mg, 4 mol.%) were dissolved in 90 mL of (653, 2.10 mmol), Pd(PPh (653, 2.10 mmol), Pd(PPh 3)4 (97 mg, 4 mol.%) and CuI (16 mg, 4 mol.%) were dissolved in 90 mL of THF/NEt 3 1:1. The mixture was stirred and heated to reflux for 3 days. The solvents were removed THF/NEt33 1:1. The mixture was stirred and heated to reflux for 3 days. The solvents were removed in 1:1. The mixture was stirred and heated to reflux for 3 days. The solvents were removed in THF/NEt in vacuum. The residue was suspended in 20 mL DCM and filtered through silica gel. The solvent vacuum. The residue was suspended in 20 mL DCM and filtered through silica gel. The solvent was vacuum. The residue was suspended in 20 mL DCM and filtered through silica gel. The solvent was was removed the crude product was further purifiedvia viacolumn columnchromatography chromatographyon on silica silica gel removed and and and the crude crude product was further purified gel removed the product was further purified via column chromatography on silica gel (petroleum benzene:ethyl acetate 3:1). A beige powder was obtained. Yield 263 mg, 28%. (petroleum benzene:ethyl acetate 3:1). A beige powder was obtained. Yield 263 mg, 28%. (petroleum benzene:ethyl acetate 3:1). A beige powder was obtained. Yield 263 mg, 28%.


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H NMR (400 MHz, CDCl3): δ(ppm) = 8.75 (ddd, 3JHH = 4.8 Hz, 4JHH = 1.9 Hz, 5JHH = 0.9 Hz, 2H, 3JHH = 4.8 Hz, 4JHH = 1.9 Hz, 5JHH = 0.9 Hz, 2H, H NMR (400 MHz, CDCl 3): δ(ppm) = 8.75 (ddd, 4 HH = 1.7 Hz, 1H, H11), 8.65 (t, 4JHH = 1.6 Hz, 1H, H4), 8.40 (d, 4JHH = 1.6 Hz, 2H, H, H3), H16), 8.68 (t, 3J 4 1 H NMRJ(400 MHz, CDCl ): δ(ppm) = 8.75 (ddd, 1.9 Hz, 5 JHH = 0.9 Hz, 3 HH = 4.8 Hz, J HH4J= 4JHH = 1.7 Hz, 1H, H11), 8.65 (t, 4JHH = 1.6 Hz, 1H, H4), 8.40 (d, H16), 8.68 (t, HH = 1.6 Hz, 2H, H, H3), 4 3 4 3 8.28 (d, JHH = 1.7 Hz, 2H, H9), 7.89 (dt, JHH = 7.9 Hz, 4 JHH = 1.1 Hz, 2H, H13), 7.81 (ddd, 4 4 J JHH = 7.9 Hz, 2H, H16), 8.68 (t, J = 1.7 Hz, 1H, H11), 8.65 (t, J = 1.6 Hz, 1H, H4), 8.40 (d, = 1.6 Hz, HH HH 4 3 4 3HH JHH = 1.7 Hz, 2H, H9), 7.89 (dt, JHH = 7.9 Hz, JHH = 1.1 Hz, 2H, H13), 7.81 (ddd, JHH = 7.9 Hz, 38.28 (d, 4JHH = 1.9 Hz, 2H, H14), 7.30 (ddd, 3JHH = 7.7 Hz, 3JHH = 4.8 Hz, 4JHH = 0.9 Hz, 2H, H15), 3.98 JHH = 7.7 Hz, 4 3 4 2H, H, H3), 8.28 (d, JHH = 1.7 Hz, 2H, H9), 7.89 JHH 3=JHH 7.9 Hz, JHH = = 0.9 Hz, 2H, H15), 3.98 1.1 Hz, 2H, H13), 7.81 3JHH = 7.7 Hz, 4JHH = 1.9 Hz, 2H, H14), 7.30 (ddd, 3JHH(dt, 4JHH = 7.7 Hz, = 4.8 Hz, (s, 6H, COOCH 3). 3J 3J 4J 3J (ddd, = 7.9 Hz, = 7.7 Hz, = 1.9 Hz, 2H, H14), 7.30 (ddd, = 7.7 Hz,3 JHH = 4.8 Hz, HH HH HH HH (s, 6H, COOCH ). 3 13C{1H} NMR (100 MHz, CDCl ): δ(ppm) = 166.1 (s,C1), 156.8 (s, C12), 150.3 (s, C16), 140.8 (s, 4J 3 = 0.9 Hz, 2H, H15), 3.98 (s, 6H, COOCH HH 13 3 ). C{1H} NMR (100 MHz, CDCl ): δ(ppm) = 166.1 (s,C1), 156.8 (s, C12), 150.3 (s, C16), 140.8 (s, C10), 137.4 (s, C14), 137.1 (s, C3), 131.6 (s, C2), 131.1 (s, C9),130.7 (s, C4), 126.4 (s, C11), 124.9 (s, C8), 13 C{1 H} NMR (100 MHz, CDCl3 ): δ(ppm) = 166.1 (s,C1), 156.8 (s, C12), 150.3 (s, C16), 140.8 (s, 3 C10), 137.4 (s, C14), 137.1 (s, C3), 131.6 (s, C2), 131.1 (s, C9),130.7 (s, C4), 126.4 (s, C11), 124.9 (s, C8), 124.1 (s, C5), 123.2 (s, C15), 121.2 (s, C13), 3). C10), 137.4 (s, C14), 137.1 (s, C3), 131.6 (s, 91.6 (s, C7), 88.3 (s, C6), 53.4 (s, CH C2), 131.1 (s, C9),130.7 (s, C4), 126.4 (s, C11), 124.9 (s, C8), 124.1 (s, C5), 123.2 (s, C15), 121.2 (s, C13), 91.6 (s, C7), 88.3 (s, C6), 53.4 (s, CH3). 124.1 (s, C5), 123.2 (s, C15), 121.2 (s, C13), 91.6 (s, C7), 88.3 (s, C6), 53.4 (s, CH3 ). 3.3.3. Syntheses and Characterization of 1,3‐Dimethyl‐5‐(ethynyl‐4‐pyridyl)isophthalate(IL3) 3.3.3. Syntheses and Characterization of 1,3‐Dimethyl‐5‐(ethynyl‐4‐pyridyl)isophthalate(IL3) 3.3.3. Syntheses and Characterization of 1,3-Dimethyl-5-(ethynyl-4-pyridyl)isophthalate(IL3) 1

1

4‐Bromopyridine hydrochloride (450 mg, 2.31 mmol), 1,3‐dimethyl‐5‐ethynylisophthalic acid 4-Bromopyridine (450 4‐Bromopyridine hydrochloride hydrochloride (450 mg, mg, 2.31 2.31 mmol), mmol), 1,3-dimethyl-5-ethynylisophthalic 1,3‐dimethyl‐5‐ethynylisophthalic acid acid (480 mg, 2.2 mmol), Pd(PPh 3)4 (100 mg, 4 mol.%) and CuI (17 mg, 4 mol.%) were dissolved in 60 mL (480 mg, 2.2 mmol), Pd(PPh ) (100 mg, 4 mol.%) and CuI (17 mg, 4 mol.%) were dissolved in 60 mL (480 mg, 2.2 mmol), Pd(PPh 3 4 (100 mg, 4 mol.%) and CuI (17 mg, 4 mol.%) were dissolved in 60 mL 3 to 80 °C for 3 days. Upon heating, the yellow solution turned light of NEt3:THF (1:1) and heated ◦ of :THF (1:1) C for of NEt NEt33:THF (1:1) and and heated heated to to 80 80 °C for 33 days. days. Upon Upon heating, heating, the the yellow yellow solution solution turned turned light light brown. Subsequently, the solvents were removed in vacuum and the residue was suspended in DCM brown. Subsequently, the solvents were removed in vacuum and the residue was suspended in DCM brown. Subsequently, the solvents were removed in vacuum and the residue was suspended in DCM ® and filtered over Celite . Chromatography on silica (CH2Cl2:ethyl acetate, 2:1) followed by solvent and filtered over Celite®®.. Chromatography on silica (CH Chromatography on silica (CH22Cl2:ethyl acetate, 2:1) followed by solvent :ethyl acetate, 2:1) followed by solvent and filtered over Celite removal yielded IL3 as a colorless solid. Yield: 545 mg, 80%. removal yielded IL3 as a colorless solid. Yield: 545 mg, 80%. removal yielded IL3 as a colorless solid. Yield: 545 mg, 80%. 1H NMR (400 MHz, CD 2Cl2): δ(ppm) = 8.63 (t, 4JHH = 1.6 Hz, 1H, H4), 8.61 (d, 2H, 3JHH = 4.6 Hz, 11 H NMR (400 MHz, CD Cl ): δ(ppm) = 8.63 (t, 44J = 1.6 Hz, 1H, H4), 8.61 (d, 2H, 33JJHH = 4.6 Hz, H NMR (400 MHz, CD 2Cl 2): δ(ppm) = 8.63 (t, JHH HH = 1.6 Hz, 1H, H4), 8.61 (d, 2H, HH = 4.6 Hz, 2 2 3 H10), 8.38 (s, 2H, H3), 7.42 (d, JHH = 4.6 Hz, 2H, H9), 3.95 (s, 6H, H11). 3 3 H10), 8.38 (s, 2H, H3), 7.42 (d, J = 4.6 Hz, 2H, H9), 3.95 (s, 6H, H11). HH = 4.6 Hz, 2H, H9), 3.95 (s, 6H, H11). H10), 8.38 (s, 2H, H3), 7.42 (d, 13C{1H} NMR (100 MHz, CD HH 2Cl2): δ(ppm) = 165.9 (s, C1), 150.5 (s, C10), 137.1 (s, C3), 131.2 (s, C2), 13 13C{ 11H} NMR (100 MHz, CD C{ H} NMR (100 MHz, CD Cl22): δ(ppm) = 165.9 (s, C1), 150.5 (s, C10), 137.1 (s, C3), 131.2 (s, C2), ): δ(ppm) = 165.9 (s, C1), 150.5 (s, C10), 137.1 (s, C3), 131.2 (s, C2), 22Cl 131.9 (s, C4), 130.0 (s, C8), 126.0 (s, C9), 123.8 (s, C5), 91.9 (s, C6), 88.7 (s, C7), 53.1(s, C11). 131.9 (s, C4), 130.0 (s, C8), 126.0 (s, C9), (s, C5), 91.9 (s, C6), 88.7 (s, C7), 53.1(s, C11). 131.9 (s, C4), 130.0 (s, C8), 126.0 (s, C9), 123.8 (s, C5), 91.9 (s, C6), 88.7 (s, C7), 53.1(s, C11). Elemental analysis (CHN): (C17H123.8 13NO4) Calc. (found): C, 69.15 (69.06); H, 4.44 (4.95); N, 4.74 Elemental H1313NO NO4) 4 )Calc. Calc.(found): (found): C, 69.15 (69.06); H, 4.44 (4.95); N, Elemental analysis analysis (CHN): (CHN): (C17 C, 69.15 (69.06); H, 4.44 (4.95); N, 4.74 17H (4.55). 4.74 (4.55). (4.55). 3.3.4. Syntheses and Characterization of 5‐Acetylthioisophthalic acid (IL4) 3.3.4. Syntheses and Characterization of 5-Acetylthioisophthalic acid (IL4) 3.3.4. Syntheses and Characterization of 5‐Acetylthioisophthalic acid (IL4)

5-Mercaptoisophthalic acid 150 mg (1 eq., 0.76 mmol) was dissolved in CH22Cl and pyridine (2 5‐Mercaptoisophthalic acid 150 mg (1 eq., 0.76 mmol) was dissolved in CH Cl2 and pyridine (2 5‐Mercaptoisophthalic acid 150 mg (1 eq., 0.76 mmol) was dissolved in CH Cl2 and pyridine (2 eq., 0.12 mL, 1.51 mmol) were cooled to 0 ◦ C. To the mixture 0.13 mL of Ac22O (1.7 eq., 1.3 mmol) were O (1.7 2eq., 1.3 mmol) were eq., 0.12 mL, 1.51 mmol) were cooled to 0 °C. To the mixture 0.13 mL of Ac eq., 0.12 mL, 1.51 mmol) were cooled to 0 °C. To the mixture 0.13 mL of Ac2O (1.7 eq., 1.3 mmol) were

Inorganics 2018, 6, 73 Inorganics 2018, 6, x FOR PEER REVIEW

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added and the mixture was stirred for 12h at room temperature. Then 50 mL of ethyl acetate was added and the mixture was stirred for 12h at room temperature. Then 50 mL of ethyl acetate was added and the organic layer was washed 3 times with 1M HCl and water each. Finally, the organic added and the organic layer was washed 3 times with 1M HCl and water each. Finally, the organic layer was dried over MgSO4 and the solvents were removed in vacuum. A beige powder was layer was dried over MgSO4 and the solvents were removed in vacuum. A beige powder was obtained. obtained. Yield 155 mg, 84%. Yield1155 mg, 84%. H NMR (400 MHz, dmso‐d6): δ(ppm) = 13.5 (s(br), 2H, H8), 8.49 (t, 4JHH = 1.6 Hz, 1H, H4), 8.12 1 H NMR (400 MHz, dmso-d6): δ(ppm) = 13.5 (s(br), 2H, H8), 8.49 (t, 4 J HH = 1.6 Hz, 1H, H4), 8.12 4 (d, 4 JHH = 1.6, 2H, H3), 2.49 (s, 3H, H7). (d, JHH 1.6, 2H, H3), 2.49 (s, 3H, H7). 13C{= 1H} NMR (100 MHz, dmso‐d6): δ(ppm) = 192.7 (s, C6), 165.8 (s, C1), 138.6 (s, C3), 132.38 (s, 13 C{1 H} NMR (100 MHz, dmso-d6): δ(ppm) = 192.7 (s, C6), 165.8 (s, C1), 138.6 (s, C3), 132.38 (s, C4), 130.6 (s, C2), 129.3 (s, C5), 30.4 (s, C7). C4), 130.6 (s, C2), 129.3 (s, C5), 30.4 (s, C7). Elemental analysis (CHS): (C10H8O5S) Calc. (found): C, 50.00 (50.02); H, 3.36 (3.62); S, 13.35 Elemental analysis (CHS): (C10 H8 O5 S) Calc. (found): C, 50.00 (50.02); H, 3.36 (3.62); S, (13.48). 13.35 (13.48). 3.3.5. Syntheses and Characterization of Macrocycle 1 3.3.5. Syntheses and Characterization of Macrocycle 1

0 ,50 -Dimethylcarboxy-2,20 ,60 ,200 -terpyridine (30 mg, 0.086 mmol) was dissolved in 40 mL of 33′,5′‐Dimethylcarboxy‐2,2′,6′,2′′‐terpyridine (30 mg, 0.086 mmol) was dissolved in 40 mL of THF/MeOH and 3.45 mL of 0.05 M NaOH and heated to reflux until TLC (ethyl acetate/petroleum THF/MeOH and 3.45 mL of 0.05 M NaOH and heated to reflux until TLC (ethyl acetate/petroleum benzene) indicated complete The solvents were were removed removed in and the residue benzene) indicated complete saponification. saponification. The solvents in vacuo vacuo and the residue i i was dissolved in 30 mL of MeOH. A purple solution of {Ru(CO)Cl(P PrPr } was dissolved in 30 mL of MeOH. A purple solution of {Ru(CO)Cl(P 2{μ‐1,4‐(CH=CH) ‐C66H H44} 3 )23)}22}{µ-1,4-(CH=CH) 22-C (90 mg, 0.082 mmol) in 40 mL of CH22Cl22 was added slowly. A yellow‐orange suspension was obtained was added slowly. A yellow-orange suspension was obtained (90 mg, 0.082 mmol) in 40 mL of CH and room temperature for 30 The solvents were removed and the residue dissolved and stirred stirred atat room temperature for min. 30 min. The solvents were removed and the was residue was ® ® in CH2 Cl2 and filtered through Celite . The solvent was stripped of the resulting orange solution dissolved in CH 2Cl2 and filtered through Celite . The solvent was stripped of the resulting orange and the obtained yellow solid was washed with MeOH, Et2 O and pentane and then dried in vacuum. solution and the obtained yellow solid was washed with MeOH, Et 2O and pentane and then dried in Yield 96 mg, 87%. vacuum. Yield 96 mg, 87%. 11H NMR (600 MHz, C 3 J = 15.3 Hz, 4JHP4 = 1.7 Hz, 4H, H NMR (600 MHz, C66D D66): δ(ppm) = 9.80 (s, 2H, H6), 8.96 (dt, ): δ(ppm) = 9.80 (s, 2H, H6), 8.96 (dt,3JHH JHP = 1.7 Hz, HH = 15.3 Hz, 3 4 5 3JHH = 8.4 Hz, 5JHHHz, 3JHH = 7.8 4H, H1), 8.36 (ddd, JHH = 8.44JHH Hz, JHH = 1.8 JHH = 1.0 Hz, 4H, H13), 7.44 (s, 8H, H4), 7.34 (dvt, = 1.8 Hz, = 1.0 Hz, 4H, H13), 7.44 (s, 8H, H4), 7.34 (dvt, H1), 8.36 (ddd, 3Hz, 4 3 4 3 3 JHH J=HH7.8 Hz, JHH = 1.0 Hz, H10), 7.17 (overlapped by solvent signal, H11), 6.73 JHH =JHH 7.7 Hz, = 1.0 Hz, H10), 7.17 (overlapped by solvent signal, H11), 6.73 (ddd, JHH(ddd, = 7.7 Hz, = 4.9 3Hz, 3JHH6.67 4JHP JHH3J=HH4.9 Hz, 3 JHH = 1.2 Hz, H12), (dt, 3 JHH = = 2.1 Hz, H2), 2.38–2.28 (m, 24H, H15), 1.32 (vq, 15.3 Hz, 4 JHP = 2.1 Hz, H2), 2.38–2.28 (m, 24H, = 1.2 Hz, H12), 6.67 (dt, = 15.3 Hz, 3JHH/HP1.32 3JHH/HP H15), (vq, 3 JHH/HP = 6.7 Hz, 72H, H16), 1.20 (vq, 3 JHH/HP = 6.7 Hz, 72H, H160 ). = 6.7 Hz, 72H, H16), 1.20 (vq, = 6.7 Hz, 72H, H16′). 13 1 13C{ 1 C{ H} NMR (150 MHz, C H} NMR (150 MHz, C66D D66): δ(ppm) = 209.8 (s, C14), 174.5 (s, C5), 160.7 (s, C7), 160.3 (s, C8), ): δ(ppm) = 209.8 (s, C14), 174.5 (s, C5), 160.7 (s, C7), 160.3 (s, C8), 156.5 (t, C1), 148.1 (s, C13), 142 (s, C6), 137.2 (s, C3), 136.0 (s, C2), 135.3 (s, C9), 126.8 (s, C11), 124.6 (s, 156.5 (t, C1), 148.1 (s, C13), 142 (s, C6), 137.2 (s, C3), 136.0 (s, C2), 135.3 (s, C9), 126.8 (s, C11), 124.6 (s, C4), 123.7 (s, C10), 122.3 (s, C11), 25.1 (vt, 33JCP =1J1CP JCP = 9.4 Hz, C15), 20.2 (s, C16‘), 19.8 (s, C16). CP = = 9.4 Hz, C15), 20.2 (s, C16‘), 19.8 (s, C16). C4), 123.7 (s, C10), 122.3 (s, C11), 25.1 (vt, 31 1 31P{ 1 6): δ(ppm) = 38.53. P{ H} NMR (162 MHz,C H} NMR (162 MHz, C6D 6D 6 ): δ(ppm) = 38.53. Elemental analysis (CHN): (C 130H NN6O 12P Ru 4) Calc. (found): C, 57.98 (56.57); H, 7.56 (7.37); N, Elemental analysis (CHN): (C130 H202 202 6O 128P 8 Ru 4 ) Calc. (found): C, 57.98 (56.57); H, 7.56 (7.37); 3.12 (3.08). N, 3.12 (3.08).


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3.3.6. Syntheses and Characterization of Macrocycle 2 3.3.6. Syntheses and Characterization of Macrocycle 2 3.3.6. Syntheses and Characterization of Macrocycle 2

1,3‐Dimethyl‐(5‐ethynylphenyl‐3,5:2,2′‐bispyridyl)‐isophthalic acid (35 mg, 0.063 mmol), 80 mL 0 -bispyridyl)-isophthalic acid (35 mg, 0.063 mmol), 80 mL 1,3-Dimethyl-(5-ethynylphenyl-3,5:2,2 1,3‐Dimethyl‐(5‐ethynylphenyl‐3,5:2,2′‐bispyridyl)‐isophthalic acid (35 mg, 0.063 mmol), 80 mL of MeOH and 2.52 mL of 0.05M NaOH were heated to reflux for 24 h. After cooling to room of of MeOH MeOH and and 2.52 2.52 mL mL of of 0.05M 0.05M NaOH NaOH were were heated heated to to reflux reflux for for 24 24 h.h. After After cooling cooling to to room room temperature, the solvent was removed and the residue was dissolved in 25 mL of MeOH. A solution temperature, thei solvent was removed and the residue was dissolved in 25 mL of MeOH. A solution temperature, the solvent was removed and the residue was dissolved in 25 mL of MeOH. A solution of {Ru(CO)Cl(Pi Pr3)2}2{μ‐1,4‐(CH=CH)2–C6H4} (90 mg, 0.082 mmol) in 30 mL of CH2Cl2 was slowly of {Ru(CO)Cl(P iPr33)22}}22{μ‐1,4‐(CH=CH) {µ-1,4-(CH=CH)2–C mg, 0.082mmol) mmol)in 30 in 30 mL mL of CH22Cl22 was was slowly of {Ru(CO)Cl(P 6H 4} (90 of CH slowly 2 –C 6H 4 } (90mg, 0.082 added to give a yellow solution. The reaction mixture was stirred for 3 days at r.t. Then the solvent added to give a yellow solution. The reaction mixture was stirred for 3 days at r.t. Then the solvent added to give a yellow solution. The reaction mixture was stirred for 3 days at r.t. Then the solvent ®. was removed in vacuo and the yellow residue was dissolved in CH2Cl2 and filtered through Celite® was removed in vacuo and the yellow residue was dissolved in CH22Cl and filtered through Celite ®. . was removed in vacuo and the yellow residue was dissolved in CH Cl22 and filtered through Celite Evaporation of the solvent and washing the residue with MeOH, Et2O and n‐pentane and drying in Evaporation of the solvent and washing the residue with MeOH, Et22O and n-pentane and drying in Evaporation of the solvent and washing the residue with MeOH, Et O and n‐pentane and drying in vacuum afforded a yellow powder. Yield: 42 mg, 46%. vacuum afforded a yellow powder. Yield: 42 mg, 46%. vacuum afforded a yellow powder. Yield: 42 mg, 46%. 1H NMR (600 MHz, C6D6): δ(ppm) = 9.28 (s, 2H, H6), 9.24 (t, 4JHH = 1.7 Hz, 2H, H15), 9.07 (d, 3JHH 11H NMR (600 MHz, C 4 J = 1.7 Hz, 2H, H15), 9.07 (d, 4JHH (s, 2H, H6), 9.24 (t, Hz, 2H, H15), 9.073J(d, H NMR (600 MHz, C66DD6): δ(ppm) = 9.28 (s, 2H, H6), 9.24 (t, HH 6 ): δ(ppm) = 39.28 HH =4J1.7 JHH = 4.7 Hz, 4H, H17), 8.26 (d, HH = 1.7 Hz, H13), 7.53 (s, = 15.2 Hz, 4H, H1), 8.90 (s, 4H, H8), 8.58 (d, 3J 3 4J 3 4 = 15.2 Hz, 4H, H1), 8.90 (s, 4H, H8), 8.58 (d, J = 4.7 Hz, 4H, H17), 8.26 (d, = 1.7 Hz, H13), J HH = 4.7 Hz, 4H, H17), 8.26 (d, J HH = 1.7 Hz, H13), 7.53 (s, = 15.2 Hz, 4H, H1), 8.90 (s, 4H, H8), 8.58 (d, HH HH HH 3JHH = 7.7 Hz, 3JHH = 7.7 Hz, 4JHH = 1.9 Hz, 4H, H19), 8H, H4), 7.22 (d, 3JHH = 7.7 Hz, H4, H20), 7.08 (td, 3J 3J 3JHH(d, 3JHH(td, 3 HH = 7.7 Hz, 4JHH 7.53 (s, 8H, H4), 7.22 = 7.7 Hz, H4, H20), 7.08 Hz, 3 JHH = 7.7 = 1.9 Hz, 4H, H19), Hz, 4 JHH = 1.9 Hz, 8H, H4), 7.22 (d, = 7.7 Hz, H4, H20), 7.08 (td, = 7.7 Hz, HH HH = J7.7 3 4 6.74 (td, JHH = 15.3 Hz, J HP = 2.1 Hz, 4H, H2), 6.67 (dd, 3JHH = 7.4 Hz, 3JHH = 4.7 Hz, 4H, H18), 2.39–2.26 3JHH6.67 4H, H19),3J6.74 (td, 3 JHH4J=HP15.3 Hz, 4 JHP = 2.1 Hz, 4H, H2), (dd, 33JJHH = 7.4 Hz, 3 JHH = 4.7 Hz, 4H, 6.74 (td, HH = 15.3 Hz, = 2.1 Hz, 4H, H2), 6.67 (dd, = 7.4 Hz, HH = 4.7 Hz, 4H, H18), 2.39–2.26 (m, H24, H22), 1.35–1.21 (m, H144, H23/H23′). 0 H18), (m, H24, H22), 1.35–1.21 (m, H144, H23/H23 ). (m, H24, H22), 1.35–1.21 (m, H144, H23/H23′). 132.39–2.26 C{11H} NMR (150 MHz, C6D6): δ(ppm) = 209.8 (t, 33JCP = 15 Hz, C21), 175.4 (s, C5), 156.3 (m, 13 13C{ (150 MHz, D66): ): δ(ppm) δ(ppm) = = 209.8 209.8 (t, (t, 3JJCP 15Hz, Hz,C21), C21), 175.4 175.4 (s, (s, C5), C5), 156.3 156.3 (m, (m, C{1H} H} NMR NMR (150 MHz, C66D = =15 CP C1/C16), 149.9 (s, C17), 140.4 (s, C14), 137.3 (s, C3), 136.4 (s, C19), 135.4 (s, C2), 135.2 (s, C9), 135.0 (s, C1/C16), 149.9 (s, C17), 140.4 (s, C14), 137.3 (s, C3), 136.4 (s, C19), 135.4 (s, C2), 135.2 (s, C9), 135.0 (s, C7), C1/C16), 149.9 (s, C17), 140.4 (s, C14), 137.3 (s, C3), 136.4 (s, C19), 135.4 (s, C2), 135.2 (s, C9), 135.0 (s, C7), 131.0 (s, C13), 129.8 (s, C6), 126.4 (s, C15), 137.3 (s, C3), 123.9 (s, C12), 122.4 (s, C18), 120.4 (s, C20), 131.0 (s, C13), 129.8 (s, C6), 126.4 (s,3 C15),1 137.3 (s, C3), 123.9 (s, C12), 122.4 (s, C18), 120.4 (s, C20), 91.6 C7), 131.0 (s, C13), 129.8 (s, C6), 126.4 (s, C15), 137.3 (s, C3), 123.9 (s, C12), 122.4 (s, C18), 120.4 (s, C20), 91.6 (s, C11), 88.9 (s, C10), 25.1 (vt, JCP = JCP = 10.0 Hz, C22), 19.9 (s, C23′), 20.1 (s, C23). 1 J = 1J= 3JCP (s, C11), (s, C10), 25.1 (vt, 3 JCP = Hz, C22), 19.9 (s, C230 ), 20.1 (s, C23). 91.6 (s, C11), 88.9 (s, C10), 25.1 (vt, = 10.0 Hz, C22), 19.9 (s, C23′), 20.1 (s, C23). CP CP10.0 31P{188.9 H} NMR (162 MHz, C6D6): δ(ppm) = 38.12. 31 1 31P{ 1 P{ H} NMR (162 MHz, C H} NMR (162 MHz, C66DD6): δ(ppm) = 38.12. ): δ(ppm) = 38.12. 6148 Elemental analysis (CHN): (C H212N4O12P8Ru4) Calc. (found): C, 61.48 (58.71); H, 7.39 (7.35); N, Elemental analysis (CHN): (C 148H NN4O 12P Ru 4) Calc. (found): C, 61.48 (58.71); H, 7.39 (7.35); N, H212 Elemental analysis (CHN): (C148 212 4O 128P 8 Ru 4 ) Calc. (found): C, 61.48 (58.71); H, 7.39 (7.35); 1.94 (1.80). 1.94 (1.80). N, 1.94 (1.80). 3.3.7. Syntheses and Characterization of Macrocycle 3 3.3.7. Syntheses and Characterization of Macrocycle 3 3.3.7. Syntheses and Characterization of Macrocycle 3

1,3‐Phenyl‐dicarboxylmethylester‐5‐ethynyl‐4‐pyridine (60 of 1,3-Phenyl-dicarboxylmethylester-5-ethynyl-4-pyridine (60 mg, mg, 1.1 1.1 eq., eq., 0.20 0.20 mmol), mmol), 8.2 8.2 mL mL of 1,3‐Phenyl‐dicarboxylmethylester‐5‐ethynyl‐4‐pyridine (60 mg, 1.1 eq., 0.20 mmol), 8.2 mL of 0.05 M NaOH (2.2 eq., 0.41 mmol) and 15 mL of THF were heated to reflux for 4 h. The solvents were 0.05 M NaOH (2.2 eq., 0.41 mmol) and 15 mL of THF were heated to reflux for 4 h. The solvents were 0.05 M NaOH (2.2 eq., 0.41 mmol) and 15 mL of THF were heated to reflux for 4 h. The solvents were removed in vacuum and the remaining solid was dissolved in 120 mL of MeOH. To the colorless removed in vacuum and the remaining solid was dissolved in 120 mL of MeOH. To the colorless removed in vacuum and the remaining solid was dissolved in 120 mL of MeOH. To the colorless solution, a purple solution of {Ru(CO)Cl(PiPr3)2}2{μ‐1,4‐(CH=CH)2–C6H4} (203 mg, 0.18 mmol) in 120 solution, a purple solution of {Ru(CO)Cl(PiPr3)2}2{μ‐1,4‐(CH=CH)2–C6H4} (203 mg, 0.18 mmol) in 120


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solution, a purple solution of {Ru(CO)Cl(Pi Pr3 )2 }2 {µ-1,4-(CH=CH)2 –C6 H4 } (203 mg, 0.18 mmol) in 120 mL of CH2 Cl2 was added over 10 min. A yellow solution was obtained and stirred at room mL of CH2Cl2 was added over 10 min. A yellow solution was obtained and stirred at room temperature for 12 h. Subsequently, the solvents were removed in vacuum and the yellow crude temperature for 12 h. Subsequently, the solvents were removed in vacuum and the yellow crude product was dissolved in CH2 Cl2 and filtered through Celite®® . The yellow filtrate was dried and product was dissolved in CH2Cl2 and filtered through Celite . The yellow filtrate was dried and washed with MeOH and n-hexane (3 × 10 mL). Drying in vacuum afforded macrocycle 3 as an orange washed with MeOH and n‐hexane (3 × 10 mL). Drying in vacuum afforded macrocycle 3 as an orange solid. Yield: 169 mg, 71% solid. Yield: 169 mg, 71% 1 H NMR (600 MHz, C D ): δ(ppm) = 9.28 (t, 4 J 3 6 HH = 1.5 Hz, 2H, H6), 9.03 (dt, J HH = 15.3 Hz, 1H NMR (600 MHz, C66 D 6): δ(ppm) = 9.28 (t, 4JHH = 1.5 Hz, 2H, H6), 9.03 (dt, 3JHH = 15.3 Hz, 4JPH = 4J (d, 4 JHH = 1.5 Hz, 2H, H8), 8.36 (m, 4H, H14) 7.51 (s, 8H, 4H), 6.75 (m, 4H, PH = 1.7 Hz, 4H, H1), 8.78 4JHH = 1.5 Hz, 2H, H8), 8.36 (m, 4H, H14) 7.51 (s, 8H, 4H), 6.75 (m, 4H, H13), 1.7 Hz, 4H, H1), 8.78 (d, 3 H13), 6.72 (dt, JHH = 15.3 Hz, 4 JPH = 2.1 Hz, 4H, H2), 2.37–2.23 (m, 24H, H16), 1.32–1.21 (m, 144H, 4JPH = 2.1 Hz, 4H, H2), 2.37–2.23 (m, 24H, H16), 1.32–1.21 (m, 144H, H17/H17′). 6.72 (dt, 30 JHH = 15.3 Hz, H17/H17 ). 13C{1H} NMR (150 MHz, C6D6): δ(ppm) = 209.7 (t, 2JCP = 13 Hz, C15), 175.0 (s, C5), 156.1 (t, 2JCP = 13 C{1 H} NMR (150 MHz, C D ): δ(ppm) = 209.7 (t, 2 J 6 6 CP = 13 Hz, C15), 175.0 (s, C5), 156.1 (t, 11 Hz, C1), 150.2 (s, C14), 137.3 (s, C3), 135.6 (s, C2), 135.3 (s, C9), 135.0 (s, C8), 130.5 (s, C7) 130.3 (s,C6), 2J = 11 Hz, C1), 150.2 (s, C14), 137.3 (s, C3), 135.6 (s, C2), 135.3 (s, C9), 135.0 (s, C8), 130.5 (s, C7) 130.3 CP 3JCP = 1JCP = 9.0 Hz, C16), 125.6 (s, C13), 124.7 (s, C4), 123.5 (s, C12), 92.4 (s, C10), 88.7 (s, C11), 25.1 (vt, (s,C6), 125.6 (s, C13), 124.7 (s, C4), 123.5 (s, C12), 92.4 (s, C10), 88.7 (s, C11), 25.1 (vt, 3 JCP = 1 JCP = 9.0 Hz, 20.0 (s, C17) 19.8 (s, C17′). 0 C16),3120.0 (s, C17) 19.8 (s, C17 ). P{1H} NMR (C6D6): δ(ppm) = 37.97. 31 P{1 H} NMR (C D ): δ(ppm) = 37.97. 6 6 Elemental analysis (CHN): (C 126H198N2O12P8Ru4) Calc. (found): C, 58.54 (58.58); H, 7.72 (8.17); N, Elemental analysis (CHN): (C126 H198 N2 O12 P8 Ru4 ) Calc. (found): C, 58.54 (58.58); H, 7.72 (8.17); 1.08 (1.01). N, 1.08 (1.01).

3.3.8. Syntheses and Characterization of Macrocycle 4 3.3.8. Syntheses and Characterization of Macrocycle 4

5-Acetylthioisophthalic acid 78 mg (1.1 eq., 33 mmol),2CO K23CO 5‐Acetylthioisophthalic acid 78 mg (1.1 eq., 33 mmol), K 45 mg (1.1 eq., 33 mmol) and 50 mL 3 45 mg (1.1 eq., 33 mmol) and 50 of MeOH stirred at room temperature. thecolorless colorlesssolution, solution,a a solution solution of of mL MeOH were were stirred for 2 for h 2at h room temperature. To To the of {Ru(CO)Cl(P {µ-1,4-(CH=CH)22‐C -C6H {Ru(CO)Cl(PiiPr Pr33)22}}22{μ‐1,4‐(CH=CH) 4} (325 mg, 30 mmol) in 140 mL of CH 2Cl 2 was added over 5 6H 4 } (325 mg, 30 mmol) in 140 mL of CH 2 Cl 2 was added over 5min. After the yellow suspension was stirred for 30 min, the solvents were evaporated. The yellow min. After the yellow suspension was stirred for 30 min, the solvents were evaporated. The yellow solid Subsequently, the the solvent solid was was then then dissolved dissolved in in CH CH22Cl Cl22 and and filtered filtered through through Celite Celite®®.. Subsequently, solvent was was removed, the yellow solid was washed with methanol and hexane. Drying in vacuum gave 4 as a removed, the yellow solid was washed with methanol and hexane. Drying in vacuum gave 4 as a yellow solid. Yield 300 mg, 78%. yellow solid. Yield 300 mg, 78%. 11 H NMR (600 Mhz, C D ): δ(ppm) = 9.27 (t, 4J 4JHH = 1.2 Hz, 2H, H6), 9.03 3(d, JHH = 15.3 Hz, 4H, H NMR (600 Mhz, C66D6): δ(ppm) = 9.27 (t, = 1.2 Hz, 2H, H6), 9.03 (d, JHH3 = 15.3 Hz, 4H, H1), 6 HH 4 3 4 3JHH 4JHP = 2.2 Hz, 4H, H2), 2.37–2.25 H1), 8.614JHH (d, = 1.2 Hz, 4H, H8), 7.50 (s, 8H, H4), 6.71 (dt, JHH = 1.2 Hz, 4H, H8), 7.50 (s, 8H, H4), 6.71 (dt, JHH = 15.3 Hz, JHP = 2.2 Hz, 4H, H2), 8.61 (d, = 15.3 Hz, 2.37–2.25 (m, 24H, H13), 1.62 (s, 6H, H11), 1.36–1.19 (m, 144H, H14/H140 ). (m, 24H, H13), 1.62 (s, 6H, H11), 1.36–1.19 (m, 144H, H14/H14′). 13 1 13C{ 1 C{ H} NMR (150 MHz, C H} NMR (150 MHz, C66D D66): δ(ppm) = 209.7 (t, ): δ(ppm) = 209.7 (t, 22JJCPCP = 13 Hz, C12), 190.8 (s, C10), 175.3 (s, C5), = 13 Hz, C12), 190.8 (s, C10), 175.3 (s, C5), 156.2 (t, 22JCP = 11 Hz, C1), 137.6 (s, C8), 137.3 (s, C3), 135.52 (s, C2), 135.50 (s, C9), 130.4 (s, C7), 129.8 (s, = 11 Hz, C1), 137.6 (s, C8), 137.3 (s, C3), 135.52 (s, C2), 135.50 (s, C9), 130.4 (s, C7), 129.8 (s, 156.2 (t, CP 3 1 3 1 C6), 124.7 (s, C4), 29.5 (s, C11) 25.1 (vt, JCP = JCP JCP = 9.0 Hz, C13), 20.0/19.9 (s, C14/C140 ). C6), 124.7 (s, C4), 29.5 (s, C11) 25.1 (vt, = 9.0 Hz, C13), 20.0/19.9 (s, C14/C14′). CP = 31 1 31P{ P{1H} NMR (162 MHz, C H} NMR (162 MHz, C66DD6): δ(ppm) = 38.09 (s). 6 ): δ(ppm) = 38.09 (s). Elemental analysis (CHN): (C116 O1414PP8Ru Elemental analysis (CHN): (C 116H196 4S42S ) Calc. (found): C, 55.05 (54.81); H, 7.81 (7.64); S, 196O 8 Ru 2 ) Calc. (found): C, 55.05 (54.81); H, 7.81 (7.64); S, 2.53 (2.32). 2.53 (2.32). Supplementary following areare available online at http://www.mdpi.com/2304-6740/6/3/73/s1, Supplementary Materials: Materials: The The following available online at www.mdpi.com/xxx/s1, Figures S1–S21: 1 H and 13 C{1 H} and 31 P{1 H} NMR spectra of all compounds, Figures S1–S21: Graphical representations of the 1 13 1 31 1 Graphical representations of the H and C{ H} and P{ H} NMR spectra of all compounds, Figures S22–S27: Figures S22–S27: ESI-MS spectra of complexes 1, 2, and 4, Figure S28: Additional packing diagrams of macrocycle 4, ESI‐MS spectra of complexes 1, 2, and 4, Figure S28: Additional packing diagrams of macrocycle 4, Figure S29: Figure S29: Association of macrocycle 4 in the crystal by hydrogen bonding, Tables S1–S3: Crystal and refinement Association of macrocycle 4 in the crystal by hydrogen bonding, Tables S1–S3: Crystal and refinement data and full lists of bond parameters of 4, Figures S30–S40: Graphical representations of the cyclic and square wave voltammograms, Figures S41–S58: the results of IR/NIR as well as UV/Vis/NIR spectroelectrochemical experiments; Figures S59–S70: EPR spectra of the di‐ and tetracations of the macrocycles at r.t. and at 78 K.


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data and full lists of bond parameters of 4, Figures S30–S40: Graphical representations of the cyclic and square wave voltammograms, Figures S41–S58: the results of IR/NIR as well as UV/Vis/NIR spectroelectrochemical experiments; Figures S59–S70: EPR spectra of the di- and tetracations of the macrocycles at r.t. and at 78 K. Author Contributions: Experimental work P.A. and M.R.R.; electrochemistry and spectroelectrochemistry: P.A.; X-ray structure analysis P.A. and M.L. Original Draft Preparation, R.F.W. and P.A. Funding: We thank the University of Konstanz and the state of Baden-Württemberg for financial support of this work. Acknowledgments: We thank Gernot Haug for the synthesis of IL4. Conflicts of Interest: The authors declare no conflict of interest.

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