MIHAELA FLONDOR 1, IOAN ROSCA 1, DOINA SIBIESCU 1, MIHAELA-
AURELIA VIZITIU 1, DANIEL-MIRCEA SUTIMAN 1,. ADRIAN-LAURENŢIU
CAILEAN 1 ...
New Coordination Compounds of Fe(III) with Organic Ligands MIHAELA FLONDOR 1, IOAN ROSCA 1, DOINA SIBIESCU 1, MIHAELA-AURELIA VIZITIU 1, DANIEL-MIRCEA SUTIMAN 1, ADRIAN-LAURENÞIU CAILEAN 1 , IGOR CRETESCU1* 1 University ,,Gh. Asachi’’ Iaºi, Faculty of Chemical and Environmental Engineering, B-dul D. Mangeron, Nr.71A, 700050, Romania
In this paper the synthesis and the study of some complex compounds of Fe(III) with ligands derived from: 2-(4-chloro-phenylsulfanyl)-1-(2-hydroxy-3,5-diiodo-phenyl)-ethanone (HL1), 1-(3,5-dibromo-2-hydroxyphenyl)-2-phenylsulfanyl-ethanone(HL2), and 2-(4-chloro-phenylsulfanyl)-1-(3,5-dibromo-2-hydroxy-phenyl)ethanone (HL3) is presented. The characterization of these complexes is based on method as: the elemental chemical analysis, IR and ESR spectroscopy, Mössbauer, the thermogravimetric analysis and X-ray diffraction. Study of the IR and chemical analysis has evidenced that the precipitates form are a complexes and the combination ratio of M:L is 1:2. The central atoms of Fe(III) presented paramagnetic properties and a octaedric hybridization. Starting from this precipitation reactions, a method for the gravimetric determination of Fe(III) with this organic ligands has been possible. Based on the experimental data on literature indications, the structural formulae of the complex compounds are assigned. Keywords: Fe(III), organic ligands, complexation compounds
Continuing the researches in the field of coordination compounds, the authors present the study of some new coordination complexes of Fe(III) using organic ligands: 2-(4-chloro-phenylsulfanyl)-1-(2-hydroxy-3,5-diiodophenyl)-ethanone (HL 1), 1-(3,5-dibromo-2-hydroxyphenyl)-2-phenylsulfanyl-ethanone (HL2), and 2-(4-chlorophenylsulfanyl)-1-(3,5-dibromo-2-hydroxy-phenyl)ethanone (HL 3). These ligands are new compounds synthesized for the first time at ,,Al. I. Cuza’’ University of Iasi [1]. The theoretical importance of this paper is justified by the synthesis and characterization of new coordination compounds of Fe(III) with organic ligands which contain complexable groups: CO and OH phenolic in the o-position. These are used for the first time as ligands in this study and practical importance is evidenced by their use as new method for gravimetric determination of Fe(III), simple and the very precise, presenting advantages in comparison with other chemical dosage methods. The synthesized compounds demonstrate the special complexable capacity of Fe(III) with the new ligands containing the phenolic and carboxilic groups. In this paper the reaction conditions, elemental chemical analysis, IR and ESR spectroscopy, Mössbauer, thermal analysis and X-Ray diffraction are presented. From experimental data and literature indications the structure of the new complexes presented in this paper with central Fe(III) atoms, is justified. Experimental part The synthesis of the studied compounds was accomplished using solutions in water and dimethylformamide mixture (1:1, v:v) of the reactants: FeCl3 (p.a.) and one of the above mentioned ligands. The synthesis took place for 90 min by stirring at room temperature, the two 200 mL solutions, both having the concentration of 0.1M. The first solution contains FeCl3 (anh. p.a.) in water and the second solution contains one of the ligands in dimethylformamide as in the following reactions:
After finishing the chemical processes, the obtained precipitates are separated by filtering, washed with a mixture of dimethylformamide – water (1:1, v:v). Then they are maintained for drying at room temperature until constant weight. The thermal stability of the obtained compounds was studied using a Q 1500D (MOM Budapest) derivatograph by registering simultaneously the three curves (TG – weight
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loss, DTG – weight loss derivate and T – temperature). The 100 mg samples are heated up to 10000C, the balance sensibility was 100; the heating rate β=100C/min; the registering sensibilities were 500µV for T, 500 µV for TG and 2.5mV for DTG. The IR absorbtion spectra of the free ligands and of the complex compounds with Fe(III) were recorded between 200 and 4000 cm -1 domain using the FTIR 660 Plus spectrometer, by KBr pelleting method. The ESR spectra of the complexes presented in this paper are recorded on solid samples with the ESR-IFA Bucharest spectrometer. From ESR spectra of the studied compounds were calculated using literature indications [9-11] the g-factor and the number of odd electrons for 1g of the analysed sample and for the central coordinated metallic atom. As etalon was used diphenylpycrylhidrazine (DPPH) and the method applied was of double graphic integration and the formula: where: Nx is the number of odd electrons of the analysed sample; Ne=2.81 . 1019 odd electrons/mL for the etalon sample. Ax and Ae are the surfaces of the ESR spectra for the sample and etalon. The g-spectroscopic splitting was calculated using formula: where: ge=2.0055 for reference sample; Hx, is the intensity of magnetic field for the sample; He= 3216.9 Gauss is the intensity of magnetic field for the reference sample. He can also be calculated from the formula: hν= ge . β . He where: h is the Planck constant; ν = 9030 MHz is the frequency of the magnetic applied field; β = 9.10-21erg/oe is the Bohr-Procopiu magneton.
The computing relations can be applied only for the case when the two curves (for the sample and etalon) are of the same type: Gauss or Lorentz. For the studied compounds the curves are of Lorentz type [2-11]. When the studied compounds are diamagnetic they don’t present ESR signal. The Mössbauer spectra of the complex compounds presented in this paper were recorded using an electrodynamic apparatus with the uniform-accelerated movement at the temperatures of 80K and 300K. As a γ radiation source was used 57Co isotope in chrome matrix. For isomer displacement values determination was used as etalon natrium-nitroprusiate: Na2[Fe(CN)5NO], that presents the values: 1.76 mm/s for ∆EQ and 0.165mm/s for δ. The characterization of the studied coordination compounds by X-Ray diffraction was made with a BrukerDiffractometer D8 ADVANCE, using a Ni-filter, a copper anode and radiation Cu-Kα (λ = 1.5 Å or λ = 0.1541 nm). The work conditions were: 36 kV tension and the intensity of 30 mA. The diffractograms of the studied compounds were registered in the range of 2θ between 2 -60°, at room temperature. The computing of the experimental data was accomplished with a DIFRAC Plus Eva program according to literature indications [12-18]. Results and discussions In table 1 are presented comparatively the results from the elemental chemical analysis calculated and from experimental values of the synthesized compounds. From the elemental chemical analysis results that the combination ratio between Fe(III) and ligands is 1:2. The experimental data are corresponding to the chemical formulae of the new complex compounds. From thermal analysis data of the compounds presented in this paper and from table 2 result that the thermal decomposition takes place in steps. There are four steps for the decomposition reactions; in the first step, a water molecule is eliminated, due to the weak bond characteristic for the crystallization water. In the second stage, the coordinated water that is more strongly bonded is eliminated. This water is not completely eliminated in this stage. Also started the elimination of half
Table 1 THE ELEMENTAL COMPOSITION OF THE STUDIED COMPOUNDS
Table 2 THE THERMAL DISTRUCTION TEMPERATURES
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molecule of water derived from OH groups bonded directly to the central Fe(III) atom. In the last step, beginning with the temperature of 200210°C, the molecular structures from the third stage are destroyed. In this stage the solid stable products and volatile compounds are formed. From the IR spectra for the formed residues resulted in the last decomposition stage results that the final solid compounds presents in there structures Fe-N and Fe-O bonds together with C=N and C-C bonds. The IR absorption spectra of the free ligands were compared with the IR spectra of the obtained complex compounds. The ligands used in the synthesis of the coordination compounds contain C=O group; it is necessary to present the vibration bands characteristic for C=O group, mainly because it is implied in the coordinative bonding with the central atom. The valence vibration of carbonyl presents the maxim value in the domain: 1850-1650 cm-1 and it is shown as a intense characteristic band. For some of other compounds, this domain is smaller. For the aliphatic aldehydes, the carbonyl band is situated in 1750-1700 cm-1 field. The nature and the place of the substituents from the benzene ring influence the position of the band corresponding to valence vibrations of C=O group. Due to the fact that the C=O group is situated at the end of the chain, only C-atom is involved in another bond, which reduces the number of force constants determining the position in the spectrum of the respectively vibration. Coordination of this group by oxygen atom with metallic atoms, displaces the vibration band of C=O group to low values of frequency, according to literature indications and with the registered spectra of the compounds presented in this paper. For the studied compounds, the vibration band is situated in 1665-1605 cm-1 domain and for the free ligands this band is situated in 1690-1645 cm-1 domain. These displacements of the vibration bands explain the coordination of central atoms with oxygen from C=O group (Fe←O=C). In the complexes spectra, a peak in the 435475 cm-1 interval appears, attributed to Fe-O bond as it is shown in table 3. The figures 1-3 present the IR absorbtion spectra of the free ligands: HL1, HL2 and HL3 (a) and of the synthesized complex compounds (b). From ESR data the spectroscopic g factor and the number of odd electrons corresponding to the central
Fe(III) atom from the studied compounds were calculated; values are presented in the table 4. From ESR spectroscopy results that the central Fe(III) atom from studied compounds contain five odd electrons in the exterior electronic sphere. From experimental data results that in the studied compounds, the central Fe(III) atom is hexacoordinated, corresponding to the d 2sp 3 hybridization type [10-12]. A lot of literature indications show that the Mössbauer spectroscopy is used in order to point out the properties of the atomic nucleous of the crystalline and molecular structure, the chemical bonds characteristics and the electronic structure of the solid compounds [7, 11, 18]. From Mössbauer spectra of the synthesized complexes, using a special computing program with a computer EC 1033; the following values for the spectra parameters are obtained: the isomeric or chemical displacement δ, the temperature displacement, the qvadrupole splitting EQ and the hyperfine magnetic splitting (table 5). From the Mössbauer spectra results that in the studied compounds the central iron atom presents the oxidation state +III and high spin value (S=5/2) fact that indicates a partial ionic character for the Fe-Ligands bonds. From the values of the EQ parameter result that the central Fe(III) atom presents an octahedrical surrounding with the disposal of electrons determined by the crystalline field theory in two sublevels t2g and eg.
In the iron complex compounds with different ligands as in this studied complex, where oxygen and nitrogen atoms are involved in the coordination process, the Mössbauer spectra indicate a small modification of the symmetry of the central atom. For the studied compound
Table 3 THE IR SPECTRAL BANDS CHARACTERISTIC FOR THE FREE LIGANDS HL1, HL2 AND HL3 AND FOR STUDIED COMPOUNDS, (cm-1)
Table 4 THE g FACTOR, Hx (GAUSS) VALUES AND THE ODD ELECTRONS NUMBER CORRESPONDING TO THE CENTRAL ATOMS FROM STUDIED COMPOUNDS 1332
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Table 5 THE MÖSSBAUER SPECTRA PARAMETERS VALUES FOR SYNTHESIZED COMPLEXES WHICH CONTAIN AS CENTRAL ATOM 57Fe
a temperature dependence of the isomer displacement is observed. This value is higher than the usual value of 0.05 mm/s . 100 °C, observed in other compounds [18-19]. This increase of the isomer displacement is in accordance with the second degree Doppler effect. This fact indicates that together with the increase of temperature from 80 to 300K and also with the increase of the oscillation movements of the Fe(III) atoms from the crystalline net, an electronic ,,s’’ type displacement of the ligand-central atom bond is observed. In conclusion we can affirm that from the Mössbauer spectra, in the studied compounds with Fe(III) are observed the following: -in the exterior sphere, there are five unparried electrons (S=5/2) that indicates the relative ionic character for the Fe-O bond; -the central atom presents an octahedrical surrounding with oxygen atom; -the quadrupole splitting is low observable in the case in which the coordination of the central atoms is realised through oxygen and nitrogen atoms and as a consequence the symmetry of the surrounding is decreased, with an ununiform distribution of electrons on the molecular orbitals from the rectangular axes; -a temperature dependence of the isomer displacement higher than usual is observed and this is in accordance with the second degree Doppler effect, that indicates together with the increase of temperature, an electronic displacement ,,s’’ type in the central atom-ligand bond is observed [10-11, 18]. From X-Ray Diffraction spectra results that the complex compounds with Fe(III) presents a highly amorphous structure, which makes impossible the X-Ray Diffraction spectrum recording [19, 20]. Further, an example of analytical determination of Fe(III), using 2-(4-chloro-phenylsulfanyl)-1-(2-hydroxy-3,5diiodo-phenyl)-ethanone (HL1) as the precipitation agent is presented [20]. Reagents -10-2 M aqueous solution of FeCl3 stabilized with dimethyl formamide -10 -2 M solution of 2-(4-chloro-phenylsulfanyl)-1-(2hydroxy-3,5-diiodo-phenyl)-ethanone (HL1) and dimethyl formamide. Working method A volume of 15-20 mL of 10-2 M FeCl3 solution is diluted at 100 mL and then treated with solution of Salmen in excess, under stirring. pH is corrected at 5 value with 0.1 N NaOH solution. After 90 min at room temperature, the yellow precipitate is filtered and washed with a mixture of C2H5OH-H2O (1:1, v:v). Then follows vacuum drying until constant weight; the obtained precipitate presents the REV. CHIM. (Bucureºti) ♦ 59 ♦ Nr. 12 ♦ 2008
chemical formula: (C14H8O2SI 2Cl)2Fe(OH) . 3H 2O. The stoichiometric factor f is 0.2968; relative error is ± 0.5. Conclusions The organic ligands derived from: 2-(4-chlorophenylsulfanyl)-1-(2-hydroxy-3,5-diiodo-phenyl)-ethanone (HL1), 1-(3,5-dibromo-2-hydroxy-phenyl)-2-phenylsulfanylethanone (HL2), and 2-(4-chloro-phenylsulfanyl)-1-(3,5dibromo-2-hydroxy-phenyl)-ethanone (HL3) reacts with Fe(III) at low acid pH and a yellow and brown precipitates are obtained which are water insoluble, stable in time at room temperature with formulae: (C 14 H 8O 2SI 2 Cl) 2 Fe(OH).3H2O(Fe-HL1); (C14H9O2SBr2)2Fe(OH).3H2O(Fe-HL2) and (C14H8O2SBr2Cl)2Fe(OH).3H2O(Fe-HL3). The obtained precipitates can be used as a possible method for gravimetric determination of Fe(III) with organic ligands. The new complex compounds synthesized in this paper were analyzed by the methods: elemental chemical analysis, thermal analysis, IR and ESR spectroscopy, Mössbauer and X-ray diffraction. From experimental data results that the synthesized precipitate is a complex with the combination ratio M:L 1:2, with central atom Fe(III) coordinated in octhaedrical structure. References 1.CASCAVAL, Al., Brevet Romania nr.89358, 30.10.1985, 6690 1h, 1987 2.PUI A., BERDAN I., CARUNTU G., COZMA D.,Rev. Chim. (Bucureºti), 51, nr.10, 2000, p. 799 3.OPRE,A L., FLONDOR, M., Polimeri de coordinaþie cu proprietãþi de semiconductori, Analele Universitãþii ,,A. Vlaicu’’ Arad, seria Chimie, fasc. Chimie ºi Protecþia Mediului, 2004, p.152 4.ROSCA, I., FLONDOR, M., SIBIESCU, D., Coordination Compounds of Mn(II) and Ni(II) with ligands derived from morpholine-carbodithioic acids, Analele Universitatii ,,Al.I.Cuza’’ Iasi, tomul XIV, nr.2, 2006, p. 83 5.FLONDOR, M., SIBIESCU, D., ROSCA ,I., Compuºi coordinativi ai Co(II) cu liganzi organici ce conþin atomi donori de oxigen, Buletin I.P.I., sectia Chimie si Inginerie Chimica, tomul LII (LVI), fasc. 3-4, 2006, p. 7 6.CONSTANTINESCU, G.C., ROSCA, I., JITARU, I., CONSTANTINESCU, C., Chimie Anorganicã ºi Analiticã. Ed.Didacticã ºi Pedagogicã, Bucureºti, 1983 7.BULHAC, I., Sinteza, proprietãþile fizico-chimice ºi structura compuºilor coordinativi cu fier, cobalt, nichel ºi cupru cu α dioxime, Tezã de doctorat habilitat, Universitatea de Stat din Chiºinãu, 2000 8.CHANDRA, S., KUMAR, U., Spectral and magnetic studies on manganese(II), cobalt(II) and nickel(II) complexes with Schiff bases, Spectrochimica Acta Part A 61, 2005, p. 219 9.BEN-SABER, S.M., MAIHUB, A.A., HUDERE, S.S., EL-AJAILY, M.M., Complexation behaviour of Schiff base toward transition metal ions, Microchemical Journal 81, 2005 p. 191 10.ROSC,A I., SUTIMAN, D., CAILEAN ,A., VIZITIU, M., SIBIESCU, D., RUSU, I., Rev. Roum. Chim., 42, 1997, p.1 11.ROSCA, I., OPREA ,L., SIBIESCU, D., Mat. Plast., 41, nr.4, 2004, p.203
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12.MADALAN, A.M., MELNIC, E., KRAVTSOV, Ch., SIMIONOV, Y.A., SCHMIDTMANN M., MULLER A., ANDRUH M., Rev. Chim. (Bucureºti), 55 nr. 9, 2004,p. 678 13.COZMA D., TATARU, V., GANJU, D., CALU, N., 50, nr. 10, 1999, p. 745 14.COZMA ,D., PUI ,A., DUCA, Al., Rev. Chim. (Bucureºti), 53, nr. 8, 2002, p. 590 15.EMANDI, A., CALINESCU, M., IFTIMIE, N., Rev. Chim. (Bucureºti), 54, nr.8, 2003, p. 661 16.STANESCU, M.D., JITARU, I., OPREA, O., JINGA ,O.A., Rev. Chim. (Bucureºti), 55, nr. 9, 2004, p. 697
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17.PUI, A.., CASCAVAL, Al., Rev. Chim. (Bucureºti), 56, 2005 , p. 861 18.FOCA N., SIBIESCU D., OANCEA S., Metode fizico-chimice aplicate în studiul combinaþiilor complexe, Ed.Tehnopress, 2006 19.KLUG P., ALEXANDER E., X-ray diffraction procedures, J. Wiley and Sonc. Inc. New York, 1974 20.FLONDOR, M., Compuºi coordinativi ai cationilor unor metale tranziþionale, Tezã de doctorat, Universitatea Tehnicã ,,Gh.Asachi’’ Iaºi, Facultatea de Inginerie Chimicã ºi Protecþia Mediului, 2007 Manuscript received: 13.11.2007
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