The ternary metal mixed ligand complexes formed by benzimidazole and N, N-bis (2-hydroxyethyl) glycine  

作　　者：贺小凤 龙腊生 毋福海 乐学义 陈小明 计亮年 周忠远 

出　　处：《Science China Chemistry》1999年第2期185-194,共10页中国科学（化学英文版）

基　　金：Project supported by the National Natural Science Foundation of China (Grant No. 29871036);the Natural Science Foundation of Guangdong Province (Grant No. 97021);the State Key Laboratory of Coordination Chemistry of Nanjing University

摘　　要：The stability constants of the ternary M(Bic)(Bzim)+ complexes, where M2+ = Cu2+, Ni2+ or Zn2+, Bic- = the anion of N, N-bis(2-hydroxyethyl) glycine and Bzim = benzimidazole, were determined by potentiometric pH titration in aqueous solution. One of them (M2+ = Cu2+) was also separately determined by spectrophotometry. The results show that these ternary complexes are stabler than expected on statistical grounds. The enhanced stability of the ternary M(Bic) (Bzim)+ complexes is attributed to the πA-πB cooperative effect between Bic- and benzimidazole. Besides, compared with Cu(Bic) (Bzim)+ and Ni(Bic) (Bzim)+, the ternary Zn(Bic) (Bzim)+ complex has relatively high stability. The crystal structure of [Cu(Bic)(Bzim)]ClO4 was determined by single crystal X-ray diffraction techniques. The copper atom has a trigonal-bipyramidal geometry, the basal plane is formed by an oxygen atom of the carboxylato group and two hydroxyl oxygen atoms, the apical position is occupied by a nitrogen atom of Bic- and a nitrogen atom of benzimidazole. The molecular structure of Cu(Bic) (Bzim)+ in aqueous solution is different from that in the crystalline state. The results of ESR and electronic spectra show that the structure of this complex is octahedron in aqueous solution.The stability constants of the ternary M（Bic）（Bzim）⁺ complexes, where M²⁺=Cu²⁺, Ni²⁺ or Zn²⁺, Bic^-=the anion of N, N-bis（2-hydroxyethyl） glycine and Bzim = benzimidazole, were determined by potentiometric pH titration in aqueous solution. One of them (M²⁺ = Cu²⁺) was also separately determined by spectrophotometry. The results show that these ternary complexes are stabler than expected on statistical grounds. The enhanced stability of the ternary M（Bic） （Bzim）⁺ complexes is attributed to the π_A-π_B cooperative effect between Bic^- and benzimidazole. Besides, compared with Cu（Bic） （Bzim）⁺ and Ni（Bic） （Bzim）⁺, the ternary Zn（Bic）（Bzim）⁺ complex has relatively high stability. The crystal structure of [Cu（Bic）（Bzim）]ClO₄ was determined by single crystal X-ray diffraction techniques. The copper atom has a trigonal-bipyramidal geometry, the basal plane is formed by an oxygen atom of the carboxylato group and two hydroxyl oxygen atoms, the apical position is occupied by a nitrogen

关 键 词：crystal structure TERNARY mixed LIGAND complex BICINE stability constant copper. 

分 类 号：O641[理学—物理化学]