Synthesis, spectroscopic and structural characterization of bis( acetato) tetrakis (imidazole) copper (II) : a model complex for DNA binding

Abstract

The complex bis(acetato)tetrakis(imidazole)copper(II), [Cu(Im)4(OAc)2] (2), has been prepared by the reaction of excess imidazole with Cu2(OAc)4 . Complex 2 exhibits a magnetic moment of 1.88 BM, consistent with one unpaired electron and the formulation of the complex as a Cu(II) monomer. The frozen-solution ESR spectrum exhibits axial symmetry with g11 and g.,i_ values of 2.221 and 2.040, respectively, and A11 (Cu) = 181x l0-4 cm- 1.The g.L signal and lowest-field component of the g11 signal exhibit 14N super-hyperfine structure that consists of nine lines with A.L (N) = 15 X 10-4 and A (N) = l0 X 10-4 cm- 1. The ESR data are consistent with the tetragonally elongated chromophore CuN4 •••02• Complex 2 crystallizes in the space group C2/c with a = 13.187(2), b = 8.591(1), c = l7.644(2) A, {3=104.13(1), V= 1938.4(5) A.3, Z = 4, Dcaic = l.556 g/cm3• The relevance of complex 2 to DNA binding of copper II) imidazole complexes is discussed..