Crystal structure, thermogravimetric analysis and electrochemical properties of the cobalt(Ⅱ) complex of【推荐论文】 .doc

精品论文Crystal structure, thermogravimetric analysis and electrochemical properties of the cobalt() complex of1-(4-methoxybenzyl)-2-(4-5methoxyphenyl)benzimidazoleYANG Hongwei, YUE Fan, WANG Jide(Key Laboratory of Oil and Gas Fine Chemicals, Ministry of Education and Xinjiang UyghurAutonomous Region, College of Chemistry and Chemical Engineering, Xinjiang University,10Urumqi, 830046)Abstract: Cobalt (II) complex of 1-(4-methoxybenzyl)-2-(4-methoxyphenyl)benzimidazole have been synthesized and characterized by IR, X-ray diffraction, thermogravimetric analysis, and cyclic voltammetry. This complex crystallized in the monoclinic space group P2/n with the cobalt atom adopting a four-coordinate distorted-tetrahedral environment, crystal of the complex: a=12.88 (Å),15b=9.83( Å),c=15.44( Å), =90°, V=1953.0(5) Å 3. The cobalt adopts a four-coordinate distorted-tetrahedral environment by two nitrogen atoms and two terminal chlorine atoms. The electrochemical characteristics have been studied by cyclic voltammetry, and the result proved that the coordination of the ligand with cobalt(II) increased the electrochemical activity of the ligand. Thecomplex was characterized by thermogravimetric analysis revealed it has good thermal stability.20Key words: Benzimidazole derivative; Schiff base; crystal structure; Co(II) Complex0IntroductionBenzimidazoles are of considerable chemical and biological interest as their derivatives have found wide use as anthelmintic agents in both human and veterinary medicine.The coordination chemistry of azoles acting as ligands in transition metal compounds has led to the extensive study25of chelating ligands incorporating benzimidazole groups for modeling biological systems 1-3.We have reported that the reaction ofp-methoxybenzaldehyde with o-phenylenediamine yielded the benzimidazole derivative (1-(4-methoxybenzyl)-2 -(4-methoxyphenyl)benzimidazole) 1 4. In order to examine the characteristics of the corresponding complexes of this ligand, the cobalt(II) complex 2 has been synthesized and characterized by X-ray diffraction, DTA-TG and cyclic30voltammetry.We report our observations in this communication.NMeONOMe1Foundations: Specialized Research Fund for the Doctoral Program of Higher Education(No. 20096501110001) Brief author introduction:YANG Hongwei(1980-),male,research field:applied chemistryCorrespondance author: WANG Jide(1958-),male,Professor,research field:applied chemistry. E-mail:awangjdyahoo.com.cn- 6 -1Experimental351.1MaterialsThe IR spectra were recorded on a Bio-Rad FTS-40 spectrophotometer.The thermogravimetric analysis of the compound was studied (35-900ºC, 10k/min) with an air/30/N2/0 flow with NETZSCH STA 449C.1-(4-methoxybenzyl)-2-(4-methoxyphenyl)benzimidazole (1).40Prepared as previously reported and characterized by IR spectroscopy and x-ray diffraction4.1-(4-methoxybenzyl)-2-(4-methoxyphenyl)benzimidazole, cobalt(II) chloride complex (2). CoCl2 (1mmol) methanol solution was added to a methanol solution containing1-(4-methoxybenzyl)-2-(4-methoxyphenyl)benzimidazole (2mmol). The solution was refluxed for454 h.After cooling to ambient temperature, blue crystals formed upon overnight standing.M.P.240-243 ºC. Anal. calc.for C44H40N4O4CoCl2: C,64.55; H,4.92; N,6.84.Found: C,64.68; H,5.18; N,6.87. IR(KBr)：(C=N) (Imid),1454 cm-1 (s); (C-N)(ph),1302 cm-1 (s); C-H (ph),3069 cm-1 (s); C-O-C(Ph-OCH3); 1027 cm-1; 819 cm-1.501.2X-ray data collectionCrystals were mounted on a Siemens P4 four-circle diffractometer, which employed graphite-monochromated MoK radiation (0.7103 Å).Intensities were collected using the 2 scan mode. Absorption corrections were applied to the data set of each crystal using the -scan technique.The structures were solved by direct methods with successive Fourier syntheses.55Full-matrix least-squares refinement on F 2 was performed using SHELXTL-97 with anisotropic thermal parameters for all non-hydrogen atoms 5-7. During data collection, three standard reflections were monitored for intensity variation.Table 1. Crystal Data and Structure Refinements for Complex 2. Empirical formula C44H40Cl2N4O4Co (2) Formula weight 818.63Temperature (K) 293(2)Crystal system MonoclinicSpace group P2/nCrystal size/mm 0.33×0.27×0.09a (Å ) 12.88 b/ Å 9.83 c/ Å 15.44/(o) 92.86V (Å 3)1953.0(5)Z 2Dcalc. (mg/ m3) 1.39Absorption coefficient(cm-1) 6.25F(000) 850Index ranges -15h14,-11k12,-15l19 range for data collection 2.01° 26.00° Parameters refined 278Goodness-of-fit 1.111Final R indices I > 2(I)R indices (all data)R1=0.0693，R2 = 0.1952R1=0.0895，R2 = 0.206960Table 2. Selected bond Lengths (Å) and Bond Angles (deg) for complex 2. bond lengths (Å)Co-N1Co-N1Co-ClCo-Cl2.052(3)2.052(3)2.2580(2)2.2580(2)Angles (º)N1-Co-N1N1-Co-Cl N1-Co-Cl N1-Co-Cl N1-Co-Cl Cl-Co-Cl C1-N1-CoC2-N1-Co110.98(2)113.02(1)107.10(1)107.10(1)113.02(1)105.59(1)129.5(2)124.4(2)1.3Electrochemical Measurements65Electrochemical measurements were carried out using traditional three-electrode system.In the fabrication of the electrodes, a mixture containing the freshly prepared complex, graphite and acetylene black (weight ratio of 8:2:1) was first mixed and grounded in an agate mortar. Then 1 wt.% PTFE solution was added to the mixture as a binder and it was pressed on a nickel substrate whose area wass about 1cm2 at 3×107 kg/cm2 for 5 min to prepare the working electrode,70(thickness 1mm). A Hg/HgO electrode was used as the reference electrode, a platinum wire (diameter 0.2mm) as the counter electrode, and 6 M KOH solutions were used as electrolytes. Cyclic votammetry measurements were carried out on a CHI 660A electrochemical workstation system (CH Instrument; Cordova, TN).The scan rate was 0.025V/s and the scan range wasbetween 1.2V0.7V.752Results and Discussion2.1X-ray structure determinationAn ORTEP drawing of 2 is shown in Fig.1.Selected bond lengths, angles and torsion angles are listed in Table 2.The cobalt adopts a four-coordinate distorted-tetrahedral80environment by two nitrogen atoms at the 3-position of the benzimidazole moieties and two terminal chlorine atoms with a cis-angle in the range of 105.6-113.0°.The dihedral angle between the two benzene rings at the 3-positions of the benzimidazole is 28.8°, and the centroiddistance between them is 4.787 Å.Two benzimidazole groups are located with a dihedral angle of 68.6°.Fig. 2 reveals that each of the benzimidazole units ofthe complex tightly overlaps85with the respective benzimidazole ring of another molecule with the identical centroid distance of4.403 Å and dihedral angle of 0°, which further stabilize this conformation.90Fig. 1. ORTEP drawing of 2 with 20% probability thermal ellipsoids showing the labeling scheme for non-H atoms.Fig. 2. ORTEP drawing of two molecules of 2 with 20% probability thermal ellipsoids (the centroid distance95between two benzene rings indicated with the dotted line 4.403 Å).1002.2Thermogravimetric AnalysisIn order to characterize 2 in terms of thermal stability, we examined the complex using TG-DTA (Fig.3).The complex was heated from 35 ºC to 900 ºC in air which produced a TG curve displaying a three step mass loss. The first occurred at 328 ºC and was ascribed to the loss of methanol. The second event, between 328 ºC and 486 ºC, may be due to the loss of anisole as it corresponds to a weight loss of 25.05%(calculated value = 25.42%).However, no endothermic peaks were observed in DTA curve. The last mass loss step at 669 ºC arose from the105110115120complete degradation of the complex.Two exothermic peaks at 552 ºC and 614 ºC in the DTA curve accompanied the decomposition process.The residue contained 8.84 % of CoO, very close to the 8.80% value expected.Fig.3. TG - DTA curve of 2.2.3Electrochemical propertiesThe cyclic voltammetry for 1 and 2 are shown in Fig. 4.The CV for 2shows three couples of redox peaks at 0.477V/0.345V, -0.302V/-0.883V, and -0.585V.The peak current was decreasing with the increasing cycle numbers but one reduction peak at 0.302V. The CV for the complex and ligand have nearly same current peak shapes except forthe peak height.It can be concluded that transport of electronic is not assigned Co3+/ Co2+ but ligand. However, a number of differences are still evident. The corresponding peak currents of the complex is larger than those of the ligand, which shows that coordination with cobalt can enhance the electrochemical activity of the ligand to a great extent. The CV for 2 indicated that the reversible process was still due to the proton transfer and deprotonation of ligand reversibly not change of structure of ligand due to the stable structure of benzimidazole.Fig. 4 .Cyclic voltammograms of 1 () and 2 (-) at 25 °C at 0.025V·s-1 scan rates, respectively.1251303ConclusionCobalt (II) complexes of 1-(4-methoxybenzyl)-2-(4-methoxyphenyl)benzimidazole have been synthesized and characterized by X-ray diffraction, thermogravimetric analysis, and cyclic voltammetry.This complexcrystallized in the monoclinic space group P2/n with the cobalt atom adopting a four-coordinate distorted-tetrahedral environment. The CV for the complex and ligand have nearly same current peak shapes exceptfor the peak height, but the coordination ofthe ligandwith Co can increase the electrochemical activity of the ligand to a great extent.135References1401451501551601651 Wang L, Meng X G, Deng Dongsheng, et al. Synthesis, temperature-controlled structures and polyphenol oxidase activities of dinuclear manganese(II) complexes with N,N,N,N-tetrakis(2-benzimidazolylmethyl)-1,4-diethylene amino glycol ether J. norg.Chim.Acta, 2012, 387: 181-185.2 Su C Y, Yang X P, Liao S, et al. Anion-controlled assembly of low-dimensional silver(I) complexes of2-(3-pyridyl)benzimidazole (PyBIm) J.Inorg. Chem. Commun. 1999, 2 (9): 383-385.3 Aderemi R O, Pardhiva G, Michael Y, et al. Manganese(II) complex of the 'tripod' ligandtris(2-benzimidazolylmethyl)amine. Seven-coordinate Mn(II) in the crystal structure J. Inorg.Chim.Acta, 1997,257(2): 279-283.4 Yang H W, Yue F, Feng S, Wang J D, et al. One-Step Synthesis and Characteristics of BenzimidazoleDerivativesJ. Chinese J. Org. Chem. 2004, 24 (7) :792-796.5 G M Sheldrick, in: H.D. Flack, L. Parkanyi, K. Simon (Eds.), Crystallographic Computing 6: A Window onModern Crystallography, Oxford University Press, New York, 1993.6 G M Sheldrick, SHELXL-97, Program for X-ray Crystal Structure Refinement, University of Göttingen, Germany, 1997.7 G M Sheldrick, SHELXTL PLUS, Siemens Analytical X-ray Instruments, Madison, WI,1990.1-(4-甲氧基苯基)-2-(4-甲氧基苯基亚甲 基）苯并咪唑-Co()配合物的晶体结构，热分析及电化学特征杨红伟，岳凡，王吉德（石油天然气精细化工教育部和自治区共建重点实验室，新疆大学化学化工学院，乌鲁木齐830000）摘要：合成了一种 1-(4-甲氧基苯基)-2-(4-甲氧基苯基亚甲基）苯并咪唑-Co()的配合物，通过 X-射线单晶衍射确定了该配合物的结构，并经红外光谱，热分析等进行表征。该晶体属 于单斜晶系，P2/n 空间群，晶胞参数为：a=12.88 (Å), b=9.83( Å), c=15.44( Å), =90°, V=1953.0(5) Å 3, 钴离子分别与两个 N 和两个 Cl 原子配位，构筑成 4 配位的变形四面体结 构。用循环伏安法研究其电化学特征结果表明：配体与 Co()的配位提高了其本身的电化 学性能。对配合物进行热分析表征揭示了配合物具有较好的热稳定性。 关键词：晶体结构；Co(II)配合物；苯并咪唑衍生物；Schiff 碱中图分类号：O614