5-(Pyridylmethylidene)-substituted 2-thiohydantoins and their complexes with CuII, NiII, and CoII: Synthesis, electrochemical study, and adsorption on the cystamine-modified gold surface
作者:E. K. Beloglazkina、A. G. Majouga、I. V. Yudin、N. A. Frolova、N. V. Zyk、V. D. Dolzhikova、A. A. Moiseeva、R. D. Rakhimov、K. P. Butin
DOI:10.1007/s11172-006-0371-3
日期:2006.6
A series of CuII, NiII, and CoII complexes with 5-(pyridylmethylidene)-substituted 2-thiohydantoins (L) were synthesized by the reactions of the corresponding organic ligands with MCl2·nH2O. The resulting complexes have the composition LMCl2 (M = Cu or Ni) or L2MCl2 (M = Co). The reactions with N(3)-unsubstituted thiohydantoins afford complexes containing four-membered metallacycles, in which the metal ion is coordinated by the S and N(3) atoms of the thiohydantoin ligand. The reactions of N(3)-substituted thiohydantoins give complexes in which the S and N(1) atoms are involved in coordination. Study by IR spectroscopy demonstrated that the pyridine nitrogen atom is not involved in coordination. Based on the results of electrochemical study of the ligands and complexes by cyclic voltammetry and calculation of their frontier orbitals by the PM3(tm) method, the mechanism of oxidation and reduction of these compounds was proposed. In the first reduction and oxidation steps, the metal atom in the copper and nickel complexes remains, apparently, intact, and these processes occur with the involvement of the ligand fragments, viz., the coordinated thiohydantoin ligand and chloride anion, respectively. In the cobalt complexes, the first reduction step occurs at the ligand; the first oxidation state, at the metal atom. Measurements of the contact angle of aqueous wetting and electrochemical study demonstrated that carboxy-containing 2-thiohydantoins and their complexes can be adsorbed on the cystamine-modified gold surface. The structures of the complexes on the surface differ from the structures of these complexes in solution.
通过相应的有机配体与 MCl2-nH2O 的反应,合成了一系列具有 5-(吡啶亚甲基)取代的 2-硫代海因(L)的 CuII、NiII 和 CoII 配合物。所得复合物的成分为 LMCl2(M = Cu 或 Ni)或 L2MCl2(M = Co)。与 N(3)-未取代的硫代海因的反应可得到含有四元金属环的配合物,其中金属离子由硫代海因配体的 S 原子和 N(3) 原子配位。N(3) 取代的硫代海因反应生成的配合物中,S 原子和 N(1) 原子参与配位。红外光谱研究表明,吡啶氮原子不参与配位。根据配体和配合物的循环伏安电化学研究结果以及 PM3(tm) 方法对其前沿轨道的计算,提出了这些化合物的氧化和还原机理。在第一个还原和氧化步骤中,铜和镍配合物中的金属原子显然保持完好无损,这些过程分别是在配体片段(即配位的硫代海因配体和氯阴离子)的参与下发生的。在钴配合物中,第一个还原步骤发生在配体上;第一个氧化态发生在金属原子上。水润湿接触角的测量和电化学研究表明,含羧基的 2-硫代海因及其配合物可以吸附在胱胺素修饰的金表面。表面络合物的结构与这些络合物在溶液中的结构不同。