A new series of vanadium-(IV) and -(V)
complexes with ligands containing functionalities including
hydroxyethyl, carboxylate, amine, pyridyl and benzimidazole have been
prepared. The crystal structures of three complexes have been
determined. All the vanadium atoms are six-co-ordinate even though
previous complexes of the diethanolamine type have contained
five-co-ordinate vanadium. The V–N (amine) bonds of the
benzimidazole complexes are significantly longer than those of pyridyl
complexes. An empirical relationship between pK
a
value of the protonated ligand and the V–N (amine) bond length
(trans to an oxo group) of the corresponding
vanadium-(IV), -(V) and
-(IV/V) complexes was observed. Spectroscopic
studies (NMR, ESR and UV/VIS) showed that the complexes remain intact in
aqueous solution. In general, the hydroxyethyl substituted vanadium
complexes are less stable than corresponding acetate substituted ones
and the benzimidazole complexes are less stable than corresponding
pyridyl complexes. The combined knowledge concerning the properties of
all these complexes provides an excellent platform to design new
vanadium complexes pertinent to biological applications.
制备了一系列新的
钒-(IV)和
钒-(V)配合物,其
配体含有羟乙基、
羧酸基、胺、
吡啶基和
苯并咪唑等官能团。三种配合物的晶体结构已经确定。所有的
钒原子都是六配位的,尽管以前的
二乙醇胺型复合物都含有五配位的
钒。
苯并咪唑络合物的 V-N(胺)键明显长于
吡啶络合物。质子化
配体的 pK a 值与相应
钒-(IV)、-(V)和-(IV/V)络合物的 V-N(胺)键长度(反式至一个氧代基团)之间存在经验关系。光谱研究(核磁共振、电子显微镜和紫外/可见分光光度计)表明,这些配合物在
水溶液中保持完整。一般来说,羟乙基取代的
钒络合物不如相应的
醋酸基取代的
钒络合物稳定,
苯并咪唑络合物不如相应的
吡啶络合物稳定。对所有这些络合物性质的综合了解为设计与
生物应用相关的新
钒络合物提供了一个极好的平台。