Syntheses, crystal structures and spectroscopic

Inorganica Chimica Acta 414 (2014) 15–20

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Syntheses, crystal structures and spectroscopic properties of cyano-bridged two-dimensional coordination polymers with 3-methylpyridazine Kansu Gör a, Günesß Süheyla Kürkçüog˘lu b,⇑, Okan Zafer Yesßilel c, Orhan Büyükgüngör d a

Eskisßehir Osmangazi University, The Institute of Science, Department of Physics, TR-26480 Eskisßehir, Turkey Eskisßehir Osmangazi University, Faculty of Arts and Sciences, Department of Physics, TR-26480 Eskisßehir, Turkey Eskisßehir Osmangazi University, Faculty of Arts and Sciences, Department of Chemistry, TR-26480 Eskisßehir, Turkey d Ondokuz Mayıs University, Faculty of Arts and Sciences, Department of Physics, TR-55139 Samsun, Turkey b c

a r t i c l e

i n f o

Article history: Received 9 December 2013 Received in revised form 17 January 2014 Accepted 20 January 2014 Available online 30 January 2014 Keywords: Cyano-bridged complex 3-Methylpyridazine complex Tetracyanonickelate(II) complex Tetracyanopalladate(II) complex Tetracyanoplatinate(II) complex

a b s t r a c t Six new two-dimensional heteropolynuclear complexes, [M(3-mpdz)2M0 (l-CN)4]n (M = Zn(II) or Cd(II); M0 = Ni(II), Pd(II) or Pt(II); 3-mpdz = 3-methylpyridazine) were synthesized and characterized by FT-IR, Raman spectroscopy, single crystal X-ray diffraction, thermal and elemental analyses techniques. The crystallographic analyses reveal that these complexes crystallize in the monoclinic system, space group C2/m. The M0 (II) ion is coordinated by four cyanide-carbon atoms in a square planar geometry and the M(II) ion exhibits a distorted octahedral coordination with two 3-mpdz ligands and four bridging cyano groups. In all the complexes, adjacent 2D layers are further extended into 3D supramolecular network through C–H  p interactions. Thermal stabilities and decomposition products of the complexes were investigated in the temperature range of 30–700 °C in air atmosphere. Ó 2014 Elsevier B.V. All rights reserved.

1. Introduction Cyanide-bridged infinite systems have been studied intensively during the last two decades [1–5]. The facility of the cyanide group to link metal ions leads to an extensive variety of structural architectures ranging from discrete polynuclear complexes to onedimensional and multidimensional arrangements. The varieties in their structures associated with their interesting functional properties, such as molecular sieves [6,7], hosts for small molecules and ions [8,9], catalysts for the production of polyols and polycarbonates [10], room temperature magnets [11,12], electrochemically tunable magnets [13,14], photo-magnetic materials [15,16] and magneto-optical effect [17], make them suitable compounds for the design of new materials. The tetracyanonickelate(II) and tetracyanopalladate(II) anions have been extensively used as a bridging metalloligand for the synthesis and design of different dimensional networks [18–28]. However, the studies of heteronuclear compounds using tetracyanoplatinate(II) as building blocks are rare [29–31]. Diazines are key building blocks used in the design, syntheses and development for biological, medicinal and chemical compounds

[32–36]. There are three isomeric diazines: the 1,2-, more commonly known as pyridazine; the 1,3-, more commonly known as pyrimidine, and the 1,4-, more commonly known as pyrazine. Pyridazine is a heteroaromatic organic compound. The pyridazine is found within a number of herbicides and the structural of several pharmaceutical drugs. The cyano complexes obtained with diazine and its derivatives were encountered rarely, in the literature [20,37]. In our previous studies, we have reported the tetracyanonickelate(II), tetracyanopalladate(II) and tetracyanoplatinate(II) complexes with mono- or bidentate ligands [20–22,30]. As a part of our continuing research on cyano complexes, we describe here the syntheses and characterizations of cyano complexes with 3methylpyridazine, [Zn(3-mpdz)2Ni(l-CN)4]n (1), [Cd(3-mpdz)2Ni(l-CN)4]n (2), [Zn(3-mpdz)2Pd(l-CN)4]n (3), [Cd(3-mpdz)2Pd(lCN)4]n (4), [Zn(3-mpdz)2Pt(l-CN)4]n (5) and [Cd(3-mpdz)2Pt(lCN)4]n (6). We characterized their structures with vibrational (FT-IR and Raman) spectroscopy, single crystal X-ray diffraction, thermal and elemental analyses techniques. 2. Experimental part 2.1. Material and Instrumentation

⇑ Corresponding author. Tel.: +90 222 2393750; fax: +90 222 2393578. E-mail address: [email protected] (G.S. Kürkçüog˘lu). http://dx.doi.org/10.1016/j.ica.2014.01.023 0020-1693/Ó 2014 Elsevier B.V. All rights reserved.

Zinc(II) chloride (ZnCl2, 96%), cadmium(II) chloride hemi(pentahydrate) (CdCl22.5H2O, 98%), nickel(II) chloride hexahydrate

16

K. Gör et al. / Inorganica Chimica Acta 414 (2014) 15–20

(NiCl26H2O, 97%), palladium(II) chloride (PdCl2, 99%), platinum(II) chloride (PtCl2, 99%), potassium cyanide (KCN, 96%) and 3-methylpyridazine (3-mpdz, 99%) were purchased and used without further purification. FT-IR and Raman spectra of 3-mpdz and the complexes were recorded in the region of 4000–250 cm1 via Perkin-Elmer FT-IR 100 spectrometer at a resolution of 4 cm1 and Bruker Senterra Dispersive Raman Microscope using the 785 nm line of a 3B diode laser, respectively. Perkin Elmer Diamond TG/DTA thermal analyzer was used to record simultaneous TG, DTG and DTA curves in the dry air atmosphere at a heating rate of 10 K min1 in the temperature range of 30–700 °C using platinum crucibles. Elemental analyses were carried out on LECO, CHNS-932 analyzer for C, H and N at the Middle East Technical University Central Laboratory in Ankara, Turkey.

dissolved in water (50 mL). To these solutions, 1 mmol of zinc(II) chloride or 1 mmol of cadmium(II) chloride hemi(pentahydrate) dissolved in water (10 mL) were added with continuous stirring approximately for 4 h at 50 °C in a temperature-controlled bath. The M[M0 (CN)4]H2O compounds obtained were filtered and dried in air. The complexes were prepared by mixing together with the 50 mL of water solution of 1 mmol of Zn[Ni(CN)4]H2O = 0.246 g, Zn[Pd(CN)4]H2O = 0.293 g or Zn[Pt(CN)4]H2O = 0.382 g, separately. To M[M0 (CN)4]H2O solutions, 3-mpdz (2 mmol, 0.188 g) dissolved in ethanol (10 mL) was added with continuous stirring and after a few minutes ammonia (5 mL, 28%) was added a few drops to resulting solution with continuous stirring approximately for 5 h at 60 °C in a temperature-controlled bath and then filtered. The resulting clear solutions were kept for crystallization at room temperature. In the meantime, the ammonia was moved away from the solutions itself. Within about a week bright crystals were obtained. The procedure for the syntheses of cadmium complexes was similar to that used for zinc complexes, except that the Zn[M0 (CN)4]H2O was used instead of Cd[M0 (CN)4]H2O [Cd[Ni(CN)4]H2O = 0.246 g, Cd[Pd(CN)4]H2O = 0.340 g or Cd[Pt(CN)4]H2O = 0.429 g]. The C, H, N analyses were carried out for the complexes and were found to fit the proposed formulae well. Elemental analysis results of all complexes were given in Supplementary Table S1.

2.2. Crystallographic analyses Diffraction experiments were carried out at 296 and 293 K on a Stoe IPDS diffractometer. The structures were solved by direct methods and refined using the programs SHELXS97 and SHELXL97 [38]. All non-hydrogen atoms were refined anisotropically by full-matrix least-squares methods [38]. The hydrogen atoms were placed in geometrically idealized positions and refined as riding atoms. The following procedures were implemented in our analyses: data collection: X-Area, cell refinement: X-Area, data reduction: X-RED [39]; program(s) used for molecular graphics were as follows: MERCURY programs [40]; software used to prepare material for publication: WINGX [41].

3. Results and discussion 3.1. Vibrational spectra 3.1.1. 3-Methylpyridazine vibrations The FT-IR spectra of 3-mpdz and the complexes, and the Raman spectra of the complexes are illustrated in Figs. S1–S6. As can be seen from these figures, the presence of the bands belonging to the ligand in the FT-IR and Raman spectra of the complexes shows the existence of 3-mpdz in the complexes. The assignments of 3-mpdz wavenumbers observed in the FT-IR and Raman spectra of the complexes are given in Table 1, together with the wavenumbers for free 3-mpdz [42]. The first detailed infrared spectra for 3-methylpyridazine was made by Ayachit et al. [43]. As can be seen in Table 1, the C–H stretching absorption of pyridazine ring m(CH)

2.3. Syntheses of the complexes K2[M0 (CN)4]H2O was prepared by mixing the stoichiometric amounts of nickel(II) chloride hexahydrate (1 mmol, 0.238 g) or palladium(II) chloride (1 mmol, 0.177 g) or platinum(II) chloride (1 mmol, 0.266 g) in water (10 mL) solutions with potassium cyanide (4 mmol, 0.260 g) in water (10 mL) solutions. These solutions were filtered and allowed to evaporate at room temperature in order to crystallize. The K2[M0 (CN)4]H2O (1 mmol) complexes (M0 , 0.259 g for Ni(II), 0.306 g for Pd(II), 0.395 g for Pt(II)) were

Table 1 The FT-IR and Raman wavenumbers of the 3-mpdz and the complexes (cm1). Assignment [42]

3-mpdz (liquid)

1 FT-IR

R

FT-IR

R

FT-IR

R

FT-IR

R

FT-IR

R

FT-IR

R

m(CH) mas(CH3) ms(CH3)

3057 w 2998 vw 2927 vw 2867 vw 1583 s 1553 w 1436 vs 1379 m 1254 m 1194 vw 1154 m 1082 m 1041 m 1005 m 943 vw 805 vs 791 vs 746 s 634 w 557 m 470 w 355 s

3056 w 2993 vw 2926 vw 2881 vw 1589 m 1568 m 1444 vs 1383 m 1256 m 1215 m 1169 w 1098 m 1040 w 1006 m 950 m 818 s 801 vs 742 s 648 w 559 m 492 w 368 s

3081 m 3019 w 2936 m – 1601 w 1580 w 1439 vw 1385 w 1266 w 1224 m 1180 w 1109 m – 1020 m – 832 m – 754 vw 661 w 574 m 478 w 329 m

3058 w 2987 vw 2925 vw 2887 vw 1588 m 1565 m 1443 vs 1381 m 1257 m 1215 m 1167 w 1095 m 1040 w 1002 m 946 m 817 s 798 vs 739 s 647 w 558 w 484 vw 363 s

3184 w 3018 w 2936 m – 1606 vw 1575 w 1455 vw 1394 w 1268 m 1226 m 1181 w 1107 m – 1017 m – 831 m – 737 vw 660 w 574 w 478 vw 320 m

3058 w 2994 vw 2929 vw 2884 vw 1589 m 1568 m 1443 vs 1382 m 1256 m 1214 m 1168 vw 1097 m 1039 w 1005 m 948 m 818 s 799 vs 741 s 648 w 559 w 491 m 368 s

3078 vw – 2933 vw – 1596 w 1574 w 1453 w 1386 m 1265 m 1221 s 1178 m 1108 s – 1018 s 994 sh 830 s – 753 w 660 m 572 s 501 m 454 m

3061 w 2985 vw 2925 vw 2888 vw 1588 m 1566 m 1443 vs 1381 w 1252 m 1214 w 1167 vw 1095 m 1039 w 1002 m 945 w 817 m 796 vs 739 m 647 w 558 w 484 w 363 s

3070 m 3017 w 2936 m – – 1573 w – 1395 vw 1266 w 1224 m 1179 w 1106 w – 1017 w – 830 m – – 658 w 573 w 492 w 447 w

3057 w 2994 vw 2929 vw 2882 vw 1588 m 1568 m 1442 vs 1382 m 1256 m 1213 w 1168 vw 1097 m 1039 m 1005 m 948 m 818 s 799 vs 741 s 648 m 559 m 505 s 367 s

3077 w – – – 1602 w 1578 w 1452 w – 1265 m 1223 m 1178 w 1110 m – 1020 w – 832 m – – 663 m 573 m – 355 m

3060 w 2989 vw 2925 vw 2882 vw 1588 m 1565 m 1442 vs 1381 m 1256 m 1213 w 1164 vw 1095 m 1038 w 1002 m 945 m 817 s 796 vs 739 s 646 m 558 m 501 s 363 s

3080 w – 2934 w – 1597 w 1572 m 1450 w 1382 m 1265 m 1221 s 1177 m 1105 s – 1015 s – 828 s – 749 w 657 m 571 s 472 vw –

das(CH3)

mring mring das(CH3) ds(CH3) m(CX) r(CH3) + c(CX)

mring d(CH) r(CH3) dring c(CH)

mring c(CH) cring dring dring c(CH)

cring

2

3

4

5

Abbreviations used: n, stretching; d, deformation; r, rocking; c, bending; s, strong; m, medium; w, weak; sh, shoulder; v, very.

6

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K. Gör et al. / Inorganica Chimica Acta 414 (2014) 15–20 Table 2 The wavenumbers (cm1) of the [M(CN)4]2 (M = Ni(II), Pd(II) or Pt(II)) vibrations in the complexes. Assignments

K2[Ni(CN)4]H2O [47]

K2[Pd(CN)4]H2O [48]

K2[Pt(CN)4]H2O [49]

1

2

3

4

5

6

A1g, m(C„N) B1g, m(C„N) Eu, m(C„N) Eu, m(C„N) Eu, m(M–C) A2u, p(M–CN) A1g, m(M–C) Eu, d(M–CN)

(2160) vs (2137) m 2122 vs 2084 w 540 w 443 w – 417 s

(2169) vs (2159) s 2135 vs 2096 w 486 w – (436) m 393 s

(2174) vs (2154) m 2136 vs 2085 sh 504 m 428 vw (479) w 407 s

(2188) vs – 2158 vs 2118 vw 559 m 448 vw – 429 vs

(2181) vs – 2151 vs 2111 vw 558 m 444 sh – 427 vs

(2204) vs (2188) m 2172 vs 2155 vw 491 m – (454) w 406 vs

(2198) vs (2182) s 2163 vs 2149 vw 484 m – (447) w 403 vs

(2214) vs (2192) m 2168 vs 2131 vw 505 m 456 sh (438) w 445 vs

(2203) vs (2180) m 2159 vs 2122 vw 501 m 453 vs (472) w 440 vs

Abbreviations used: s strong, m medium, w weak, sh shoulder, v very. The symbols m, d and p refer to valence, in-plane and out-of-plane vibrations, respectively. Raman bands are given in parentheses.

in the free 3-mpdz occurs as a weak band at 3057 cm1. In the complexes; the same modes are observed about at 3058 cm1 wavenumber value in FT-IR spectra. Infrared bands of 3-mpdz ligand observed at 2998 and 2927 cm1 values are assigned to the m(CH3) asymmetric and symmetric stretching frequencies, respectively. The absorption bands of the m(CH3) groups in all complexes are observed in the frequency range of 2994–2925 cm1, and these bands shifted to lower frequency when compared to free 3-mpdz ligand. mring modes of free 3-mpdz are found in 1583– 805 cm1 range and the same modes are observed in 1589– 817 cm1 range in FT-IR spectra of the complexes. It is clear from Table 1 that some of the vibrational modes of ligands in the complexes have been increased in wavenumbers when compared to free ligands. These shifts can be explained as the coupling of the internal modes of the ligand molecules. When the aromatic ring nitrogen involves complex formation, certain ring modes, particularly modes of 1600–1400 cm1, increase in value both due to the coupling with M–Nligand bond vibrations [44,45] and due to alterations of the ring force field [46]. 3.1.2. [M0 (CN)4]2 group vibrations The m(CN) vibrations are the most important absorption bands for complexes since the m(CN) vibrational peaks in the FT-IR and Raman spectra are used to reveal the bridging formation in the

polymeric complexes. This vibration may easily be determined in the range of 2200–2000 cm1. The vibrational wavenumbers for [M0 (CN)4]2 group in K2[M0 (CN)4]H2O and in 1–6 are presented in Table 2, together with the vibrational assignments of Na2[Ni(CN)4] [47], [Pd(CN)4]2 [48] and [Pt(CN)4]2 [49]. m(CN) vibration mode is observed at 2122 cm1 as a strong and sharp band in FT-IR spectrum of the mononuclear K2[Ni(CN)4] complex. This vibration mode is observed at 2135 and 2136 cm1 for K2[Pd(CN)4]H2O and K2[Pt(CN)4]H2O complexes, respectively. These positions are observed at 2080 cm1 in ionic KCN as a single absorption band [50] with respect to the CN stretching. This stretching vibration is observed at 2158 cm1 (for 1), 2152 cm1 (for 2), 2172 cm1 (for 3), 2163 cm1 (for 4), 2168 cm1 (for 5) and 2159 cm1 (for 6) as strong absorption band. The [M0 (CN)4]2 vibrations in all complexes are found at higher wavenumber than [M0 (CN)4]2 vibrations in K2[M0 (CN)4]H2O salts. Such wavenumber shifts have been observed for some Hofmann type complexes [20,46], in which all of the CN groups are coordinated. These results are in good agreement with the structural data presented. This situation is explained as the mechanical coupling of the internal modes of [M0 (CN)4]2 with the M0 -NC vibrations [51]. The [M0 (CN)4]2 anion possesses ideally D4h symmetry and, thus, will have sixteen fundamental vibrations (2A1g, 1A2g, 2B1g, 2B2g, 1Eg, 2A2u, 2B2u, and 4Eu) [50,52]. Of these, A2u and Eu are infrared

Table 3 Crystallographic data and structure refinement parameters for complexes 1–6. Complex

1

Empirical formula Color/shape Formula weight T (K) k (Å) Crystal system Space group a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z Absorption coefficient (mm1) Dcalc (Mg m3) hmax (°) Reflections measured Reflections independent Absorption correction Refinement method R [I > 2r(I)] wR [I > 2r(I)] S Dqmax (e Å3) Dqmin (e Å3)

C14H12N8ZnNi C14H12N8CdNi light yellow/prism light yellow/prism 416.40 463.43 296 296 Mo Ka/0,71073 monoclinic monoclinic C2/m C2/m 16.611 (4) 16.611 (4) 7.4997 (11) 7.4997 (11) 6.6052 (16) 6.6052 (16) 90 90 96.612 (19) 96.612 (19) 90 90 817.4 (3) 817.4 (3) 2 2 2.63 2.46 1.692 1.883 26.5 26.5 2887 2665 920 916 X-RED32, Stoe & Cie, 2002 [39] Full-matrix least-squares on F2 0.047 0.019 0.098 0.056 1.11 1.107 0.80 0.57 0.43 0.46

2

3

4

5

6

C14H12N8ZnPd colorless/prism 464.09 293

C14H12N8CdPd colorless/prism 511.122 293

C14H12N8ZnPt colorless/prism 552.78 293

C14H12N8CdPt colorless/prism 599.81 293

monoclinic C2/m 16.5772 (19) 7.6763 (7) 6.7095 (8) 90 96.446 (9) 90 848.40 (16) 2 2.49 1.817 26.5 3024 953

monoclinic C2/m 16.8405 (13) 7.8819 (6) 6.8858 (6) 90 98.692 (6) 90 903.49 (13) 2 2.18 1.879 26.5 6794 1010

monoclinic C2/m 16.5949 (13) 7.6623 (5) 6.7225 (5) 90 96.021 (7) 90 850.08 (11) 2 9.64 2.163 26.5 6218 953

monoclinic C2/m 16.8396 (13) 7.8749 (5) 6.9033 (5) 90 98.057 (6) 90 906.41 (11) 2 8.89 2.198 26.5 3443 1011

0.018 0.040 1.17 0.27 0.58

0.017 0.037 1.14 0.34 0.35

0.012 0.028 1.05 0.69 0.68

0.012 0.030 1.08 0.43 0.49

(9) (9) (6) (6) (6) (6)

(16) (10) (10)

Symmetry codes: (i) 1  x, y, 1  z; (ii) 1  x, 1  y, 1  z; (iii) x, 1  y, z; (iv) 1  x, 2  y, 2  z; (v) 1  x, y, 2  z; (vi) x, 2  y, z for 1; (i) 1  x, y, 1  z; (ii) x, 1  y, z; (iii) 1  x, 1  y, 1  z; (iv) 1  x, 2  y, 2  z; (v) 1  x, y, 2  z; (vi) x, 2  y, z for 2; (i) 1  x, y, 1  z; (ii) 1  x, 1  y, 1  z; (iii) x,1  y, z; (iv) 1  x, 2  y, 2  z; (v) x, 2  y, z; (vi) 1  x, y,2  z for 3 and 4; (i) 1  x, y, 1  z; (ii) 1  x,  y, 1  z; (iii) x,  y, z; (vii) 1  x, 1  y,  z; (viii) 1  x, y,  z; (ix) x, 1  y, z for 5 and 6.

(6) (6) (11) (11)

N1i–Cd1–N1ii N1i–Cd1–N1 N1ii–Cd1–N1 N1i–Cd1–N2 N1–Cd1–N2 C1viii–Pt1–C1vii C1viii–Pt1–C1 C1vii–Pt1–C1 (9) (9)

87.62 92.38 180.0 87.80 92.20 92.09 87.91 180.0 N1i–Zn1–N1 N1i–Zn1–N1ii N1–Zn1–N1ii N1i–Zn1–N2 N1–Zn1–N2 C1viii–Pt1–C1vii C1viii–Pt1–C1 C1vii–Pt1–C1 (10) (10)

180.0 88.26 91.74 180.0 91.87 88.13 87.31 92.69 C1iv–Pd1–C1 C1iv–Pd1–C1v C1–Pd1–C1v N1ii–Cd1–N1 N1ii–Cd1–N1i N1–Cd1–N1i N1ii–Cd1–N2 N1–Cd1–N2 92.32 (9) 180.0 87.68 (9) 180.00 (5) 92.36 (8) 87.64 (8) 92.07 (6) 87.93 (5) C1v–Pd1–C1 C1–Pd1–C1iv C1–Pd1–C1vi N1ii–Zn1–N1 N1ii–Zn1–N1i N1–Zn1–N1i N1–Zn1–N2 N1i–Zn1–N2 (12)

91.79 180.0 88.21 88.74 91.26 180.0 91.50 88.50 180.000 (1) 91.8 (2) 88.2 (2) 92.62 (18) 87.38 (18) 180.00 (13) 92.42 (13) 87.58 (13) Bond angles C1–Ni1–C1iv C1–Ni1–C1vi C1–Ni1–C1v N1ii–Zn1–N1i N1–Zn1–N1i N1iii–Zn1–N1i N1–Zn1–N2 N1i–Zn1–N2

1.8004 (19) 2.2770 (18) 2.294 (2) C1–Ni1 N1–Cd1 N2–Cd1 1.866 (4) 2.143 (3) 2.198 (5)

C1vi–Ni1–C1 C1iv–Ni1–C1 C1–Ni1–C1v N1–Cd1–N1i N1–Cd1–N1ii N1i–Cd1–N1ii N1–Cd1–N2 N1i–Cd1–N2

C1–Pt1 N1–Cd1 N2–Cd1 1.9848 (19) 2.3170 (16) 2.357 (2) C1–Pd1 N1–Cd1 N2–Cd1 1.9879 (16) 2.1361 (15) 2.195 (2)

4 3 2

Bond lengths C1–Ni1 N1–Zn1 N2–Zn1

Thermal behaviors of the complexes were studied by TG, DTG and DTA in the temperature range 30–700 °C in the dry air atmosphere. The thermal decompositions of the all complexes proceed in two stages. Thermal decomposition curves of 1 and 2 are presented in Figs. S11a and S11b, respectively. The complexes 1 and 2 are thermally stable up to 100 and 153 °C, respectively, and then begin to decompose. The first stage between 100– 262 °C for 1 and 153–317 °C for 2 correspond to release of two 3-mpdz, which are accompanied by endothermic DTA peaks at 209 °C for 1 and 296 °C for 2. The mass loss values of 45.99%

1

2.4. Thermal analyses

Table 4 The selected bond lengths (Å) and angles (°) of the complexes.

Crystallographic data of the complexes are listed in Table 3, selected bond lengths and angles are given in Table 4. The molecular structures of the complexes, along with the atom-numbering schemes are shown in Figs. 1, S7 and S8, respectively. The crystallographic analyses reveal that the complexes crystallize in the monoclinic crystal system, space group C2/m. The M0 (II) (M0 = Ni, Pd and Pt) atoms are located on inversion centers and each M0 (II) atom is coordinated in a distorted square-planar geometry by the four symmetry related C atoms from four cyano ligands. The coordination sphere of the M(II) ion exhibits a distorted octahedral geometry. The M(II) (M = Zn and Cd) center is coordinated by two 3-mpdz and four cyano ligands. The equatorial plane has four N atoms of four symmetry related cyano ligands, while the apical position is occupied by two nitrogen atoms of two 3-mpdz. In all complexes the metal (M) atoms are located on inversion centres and surrounded by four bridged C„N groups. The bridging M–NCN bond lengths are found as Zn1–[email protected](4) for 1, Cd1–[email protected](2) for 2, Zn1–[email protected](2) for 3 Cd1–[email protected](1) for 4, Zn1–[email protected](1) for 5 and Cd1–[email protected](1) Å for 6. The M–N(„C) bond lengths are at the same values for four N atoms. Therefore, one m(C„N) absorption band are observed in the FT-IR spectra for all complexes (2158 cm1 for 1, 2152 cm1 for 2, 2172 cm1 for 3, 2163 cm1 for 4, 2168 cm1 for 5 and 2159 cm1 for 6). The complexes 1–6 have similar network to the previously reported [Cd(H2O)(2mpz)Ni(l-CN)4]n (2mpz = 2-methylpyrazine) [20], [Cd(N-Meim)2Pd(l-CN)4]n (N-Meim = N-methylimidazole) [22] complexes. The crystal packing of the complexes are stabilized through the interlayer C–H  p interactions, resulting in a 3D framework (Figs. 2, S9 and S10). The C–H  Cg contact distances and angles between the centroid of pyridazine ring and the methyl groups of the pyridazine rings are 3.193 Å and 124.37° (for 1), 3.246 Å and 122.10° (for 2), 3.039 Å and 152.30° (for 3), 3.201 Å and 148.06° (for 4), 3.057 Å and 150.04° (for 5) and 3.194 Å and 151.61 (for 6), respectively. This weak C–H  p interaction plays a major role in constructing 3D network.

5

2.3. Structural analyses

C1–Pt1 N1–Zn1 N2–Zn1

1.9825 (19) 2.1325 (16) 2.199 (2)

6

1.981 (2) 2.3166 (18) 2.362 (3)

active, while A1g, B1g, B2g, and Eg are Raman active. The A2g and B2u vibrations are inactive. No B2g modes were observed. The A1g and B1g cyano stretching modes in the Raman spectra of the complexes are observed in 2204 and 2188 cm1 (for 3), 2198 and 2182 cm1 (for 4), 2214 and 2192 cm1 (for 5), 2203 and 2180 cm1 (for 6), respectively. The A1g cyano stretching modes of the 1 and 2 are observed in 2188 and 2181 cm1 respectively. The B1g stretching modes of the complexes 1 and 2 are not observed in the Raman spectra. In the low wavenumber region of the FT-IR spectra, M0 –CN bending bands are observed for complexes. This in-plane bending vibration band, d(M0 –CN) shifts to higher frequency support the m(CN) stretching vibration band. Such frequency shifts have been observed for the other ion pair charge transfer complexes [53,54].

91.90 (10) 88.10 (10) 180.0 87.17 (7) 92.83 (7) 91.64 (11) 88.36 (11) 180.00 (14)

K. Gör et al. / Inorganica Chimica Acta 414 (2014) 15–20

C1–Pd1 N1–Zn1 N2–Zn1

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Fig. 1. The molecular structures of 1 (a) and 2 (b) showing the atom numbering scheme ((i) 1  x, y, 1  z; (ii) 1  x, 1  y, 1  z; (iii) x, 1  y, z; (iv) 1  x, 2  y, 2  z; (v) 1  x, y, 2  z; (vi) x, 2  y, z; (vii) x, y,  1+z; (viii) x, y  1, z; (ix) x, y  1, z  1) for 1; ((i) 1  x, y, 1  z; (ii) x, 1  y, z; (iii) 1  x, 1  y, 1  z; (iv) 1  x, 2  y, 2  z; (v) 1  x, y, 2  z; (vi) x, 2  y, z; (vii) x, y  1, z; (viii) x, y  1, z  1; (ix) x, y, z  1) for 2.

(Calcd. 45.21%) for 1 and 39.54% (Calcd. 40.61%) for 2 are in good agreement with the calculated mass loss value of two 3-mpdz molecules. The following stage is related with the exothermic burning of four CN groups in the 262–461 °C temperature range for 1 and 317–405 °C temperature range for 2. (DTGmax = 448 °C for 1 and

Fig. 2. C–H  p interactions in 1 (a) and 2 (b).

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DTGmax = 387 °C for 2). The final decomposition products were identified as, ZnO + NiO and CdO + NiO [(Found (Calcd.)), (33.89 (37.48)), (45.73 (43.82))], respectively. [Zn(3-mpdz)2Pd(CN)4] (3) complex is thermally stable up to 147 °C (Fig. S12a). The first stage between 147 and 288 °C corresponds to the endothermic elimination two 3-mpdz ligands with a mass loss of 38.75% (calcd. 40.55%). Four cyano ligands burn in the second stage with a strong exothermic peak on the DTG curve (DTGmax = 406 °C) between 288 and 437 °C with a mass loss of 18.63% (calcd. 22.42%). The thermal decomposition products were identified as ZnO + PdO. [Cd(3-mpdz)2Pd(CN)4] (4) complex is thermally stable up to 184 °C (Fig. S12b). Two 3-mpdz ligands separate in the first stage with an endothermic peak on the DTA curve (DTGmax = 295 °C) between 184 and 323 °C with a mass loss of 36.04% (calcd. 36.82%). In the second stage, a strong exothermic peak is observed on the DTA curve (DTGmax = 396 °C) between 323 and 418 °C with a mass loss of 15.22% (calcd. 20.36%). This peak is associated with decomposition and burning of the four cyano ligands. The thermal decomposition products were identified as CdO + PdO. [Cd(3-mpdz)2Pt(CN)4] (6) complex is thermally stable to 152 °C (Fig. S13). The endothermic peak from 152 to 357 °C corresponds to the loss of two 3-mpdz ligands (found, 31.05%; calcd. 31.38%). An exothermic peak occurs from 357 to 468 °C (DTGmax = 444 °C), which is the burning of four CN groups. The mass loss is 15.46% (calcd. 17.35%) for this stage. The thermal decomposition products were identified as CdO + Pt. 4. Conclusion In this work, six cyano-bridged heteropolynuclear complexes with 3-methylpyridazine have been synthesized under similar synthetic conditions. The M0 (II) (M0 = Ni, Pd or Pt) ions are coordinated by four carbon atoms from the cyano ligands in a square-planar geometry. The M(II) (M = Zn or Cd) ions adopt a slightly distorted octahedral coordination geometry, completed by six N atoms from two 3-mpdz and four bridging cyanide ligands. The complexes exhibit 2D sheet-like structure and are further extend into threedimensional supramolecular network through intensive C–H  p interactions. These interactions play an important role in the construction of the supramolecular networks. Acknowledgement This work was supported by the Research Fund of Eskisehir Osmangazi University. Project number: 201219A109. Appendix A. Supplementary material CCDC 883800, 883801, 974232, 974231, 974233, 974234 contain the supplementary crystallographic data for compounds 1–6, respectively. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/ data_request/cif. Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/ j.ica.2014.01.023. References [1] K.R. Dunbar, R.A. Heintz, Prog. Inorg. Chem. 45 (45) (1997) 283. [2] M. Verdaguer, A. Bleuzen, V. Marvaud, J. Vaissermann, M. Seuleiman, C. Desplanches, A. Scuiller, C. Train, R. Garde, G. Gelly, C. Lomenech, I. Rosenman, P. Veillet, C. Cartier, F. Villain, Chem. Rev. 192 (1999) 1023.

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