Novel trans-dioxorhenium complex with imidazo[1,2a]pyridine ligand - Synthesis, spectroscopic and electrochemical characterization, X-ray crystal structure and DFT calculations

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• 作者：B. Machura^a ; M. Wolff^a ; ^{mwolff@us.edu.pl} ; D. Tabak^b ; Y. Ikeda^c ; K. Hasegawa^c
• 关键词：Dioxorhenium(V) complex ; X-ray crystal structure ; DFT calculations ; Electrochemistry ; Cyclic voltammetry
• 刊名：Polyhedron
• 出版年：2012
• 期刊代码：87_02775387
• 类别：ch
• 出版时间：30 May, 2012
• 卷：39
• 期：1
• 页码：76-84
• 文件大小：1077 K

摘要

The reaction of [ReO₂(py)₄]Cl with imidazo[1,2a]pyridine has been examined and a novel dioxorhenium(V) complex - [ReO₂(impy)₄]Cl路MeCN路2H₂O with trans-[OReO]⁺ core has been obtained. The X-ray crystal structure of the complex has been determined and the electronic structure has been examined using the density functional theory (DFT) method. The UV-Vis absorption spectrum of the complex has been interpreted on the basis of the results of time-dependent DFT (TDDFT) calculations. Electrochemical reaction of [ReO₂(impy)₄]⁺ in CH₃CN solution containing tetra-n-butylammonium perchlorate as a supporting electrolyte has been studied using cyclic voltammetry at 25 掳C. Cyclic voltammograms show one redox couple around 0.156 (E_pa) and 0.080 V (E_pc) [versus ferrocene/ferricenium ion redox couple, (Fc/Fc⁺)]. Potential differences between two peaks (螖E_p) at scan rates (v) in the range from 0.04 to 0.20 V s^鈭? are ca. 75 mV, which is almost consistent with the theoretical 螖E_p value (59 mV) for the reversible one electron transfer reaction at 25 掳C. The ratios of anodic peak currents to cathodic ones are in the range from 4.76 (v = 0.04 V s^鈭?) to 3.11 (v = 0.20 V s^鈭?) and the (E_pa + E_pc)/2 value is constant, 0.118 卤 0.001 V versus Fc/Fc⁺, regardless of the scan rate. Spectroelectrochemical experiments have also been carried out by applying potentials from 0.009 to 0.159 V versus Fc/Fc⁺ with an optically transparent thin layer electrode. It was found that the UV-Vis absorption spectra show clear isosbestic points at 218.9, 248.3 and 292.8 nm, and that the electron stoichiometry is evaluated as 1.04 from the Nernstian plot. These results indicate that the [ReO₂(impy)₄]⁺ complex is oxidized quasi-reversibly to the [ReO₂(impy)₄]²⁺ complex.