Oxovanadium(iv and v) and copper(ii) complexes of N-salicyl-glycylglycine and N-salicyl-glycylglycylglycine
作者:João Costa Pessoa、Isabel Correia、Tamás Kiss、Tamás Jakusch、Margarida M. C. A. Castro、Carlos F. G. C. Geraldes
DOI:10.1039/b206835b
日期:——
By reaction of salicylaldehyde and GlyGly or GlyGlyGly, followed by reduction with NaBH4, N-salicyl-glycylglycine 1 and N-salicyl-glycylglycylglycine 2, the reduced Schiff bases H2sal-RGG and H2sal-RGGG, containing the GlyGly or GlyGlyGly moities, are prepared and characterised. Their acid–base properties and complexation with VIVO2+ and CuII are studied by pH-potentiometry, visible absorption and EPR spectrometries, and the protonation and complex formation constants are determined. Vanadium and copper complexes are also prepared and characterised. Differences in the metal binding abilities of 1 and 2 are found. Amide deprotonation is proved but its extent depends on the system, being particularly important in the M–H2sal-RGG systems with the formation of the (O-phenolate, N-amine, N-amide, COO−) (6+5+5)-membered joined chelate system. Depending on the system, at physiological pH this binding mode and/or 2 × (O-phenolate, N-amine) are dominant. The aminophenolate chelates formed with sal-RGG and sal-RGGG behave as anchoring donor sites and the ML and ML2 complexes, involving O-phenolate, N-amine chelation, form in higher relative concentration than in the corresponding M–GlyGly or M–GlyGlyGly systems. Moreover, while for the VIVO–H2sal-RGG system the N-amide deprotonation/co-ordination is strongly promoted, it is not so favoured in the CuII–H2sal-RGG and CuII–H2sal-RGGG systems. The increased stability induced by the additional O-phenolate donor is particularly relevant for sal-RGG and hydrolysis of the MLH−1 complexes starts several pH units higher than in the GlyGly systems. In contrast to VIV, the VV complexes formed with sal-RGGG were found to be more stable than those of sal-RGG.
通过水杨醛与GlyGly或GlyGlyGly反应,然后用NaBH4还原,N-水杨酰-甘氨酰甘氨酸1和N-水杨酰-甘氨酰甘氨酰甘氨酸2,制备含有GlyGly或GlyGlyGly部分的还原希夫碱H2sal-RGG和H2sal-RGGG并有特点。通过 pH 电位法、可见光吸收和 EPR 光谱研究了它们的酸碱性质以及与 VIVO2+ 和 CuII 的络合,并测定了质子化和络合物形成常数。还制备并表征了钒和铜络合物。发现1和2的金属结合能力存在差异。酰胺去质子化已被证明,但其程度取决于系统,在 M–H2sal-RGG 系统中尤其重要,可形成 (O-酚盐、N-胺、N-酰胺、COO−) (6+5+5 )-成员加入螯合系统。根据系统的不同,在生理 pH 值下,这种结合模式和/或 2 ×(O-酚盐,N-胺)占主导地位。与 sal-RGG 和 sal-RGGG 形成的氨基酚螯合物充当锚定供体位点,并且涉及 O-酚盐、N-胺螯合的 ML 和 ML2 复合物以比相应的 M–GlyGly 或 M–GlyGlyGly 更高的相对浓度形成系统。此外,虽然对于 VIVO–H2sal-RGG 系统,N-酰胺去质子化/配位得到了强烈促进,但在 CuII–H2sal-RGG 和 CuII–H2sal-RGGG 系统中并不那么受欢迎。额外的 O-酚盐供体引起的稳定性增加与 sal-RGG 特别相关,并且 MLH−1 复合物的水解起始的 pH 值比 GlyGly 系统高几个单位。与 VIV 相比,发现与 sal-RGGG 形成的 VV 复合物比 sal-RGG 更稳定。