Abstract
Two new artificial peptides with histidine side chains, namely N-methyl N,N'-bis(Im-bzl-l-histidylmethylestermethyl)amine L1 and N,N',NaEuro(3),NaEuro '-tetrakis(Im-bzl-l-histidylmethyl-estermethyl)ethylene diamine L2 have been synthesized and were shown to form stable zinc complexes [L1Zn(H2O)(2)](ClO4)(2) 1 and [L2Zn(2)(H2O)(3)](ClO4)(4) 2, respectively. Solution studies (pH-(NMR)-N-1 titrations) of the ligand L2 in the presence of zinc ions were also reported. The catalytic activity of zinc complex species 1 and 2 as structural phosphotriestrase models were tested on the hydrolysis/detoxification of p-nitrohenl diphenylphosphate (p-NPDPP). From the correlation between the pH-rate profiles and the species distribution curves, the catalytically active species could be identified. On the basis of R-dependence as well as the rate acceleration of each complex, the possibility of cooperative action of zincs in dinuclear zinc complex is debated.