Reinvestigation of the copper(II)脙脙脙脙脙脙carcinine equilibrium system: 脙脙脙脙脙脙two-dimensional脙脙脙脙脙脙 EPR simulation and NMR relaxation studies for determining the formation constants and
摘要
The equilibria and solution structure of complexes formed between copper(II) and carcinine (脦脦-alanyl-histamine) at 2脦脦脦pH脦脦脦11.2 have been studied by EPR and NMR relaxation methods. Beside the species that have already been described in the literature from pH-potentiometric measurements, several new complexes have been identified and/or structurally characterized. The singlet on the EPR spectrum detected in equimolar solutions at pH 7, indicates the formation of an oligomerized Formula Not Shown complex, with {NH2,Nim} coordination. The oligomerization is probably associated with the low stability of the ten-membered macrochelate ring, which would form in the mononuclear complex CuL2+. In presence of moderate excess of ligand the formation of four new bis-complexes ( Formula Not Shown, n