Solution and solid state investigation ofthe Cu(II)-N-acetyl-L-glutamine system and its N-methylimidazole adduct.

The interactions of N-acetyl-L-glutamine (AcglnH) with copper(II) ion in aqueous and water-methanol (50% v/v) solutions and in solid state have been investigated. It was found that the N-acetyl-L- glutaminate anion (Acgln) is unable to form stable complexes in solution on varying the pH values, before copper(II) hydroxyde precipitation occurs. In the solid state two compounds of the formulas Cu(Acgln)2·2H2O and Cu(Acgln)2(MeIm)2·2H2O (MeIm = N-methylimidazole) are separated; for the latter complex the crystal and molecular structure was determined by means of the single crystal X-ray diffraction method. The compound crystallizes in the monoclinic space group C2, with cell dimensions: a = 15.606(7), b = 7.353(2), c = 13.951(2) Å, β = 110.69(3)° and Z = 2. The structure was solved by conventional Patterson and Fouder methods and refined by full-matrix least-squares to an R value of 0.026. The structure consists of [Cu(Acgln)2(Me- Im)2] units and uncoordinated watet molecules. The Cu(II) atom lying on the twofold axis exhibits a square-planar N2O2 environment from ligation by two symmetry-related carboxytate oxygens and N-methylimidazole nitrogens. The second non- bonding carboxylate oxygens are 2.813(3) Å from the Cu(II) atom and both are placed under the coordination plane. Spectroscopic and thermal results agree with the crystal stmcture, while for binary Cu(Acgln)2·2H2O a CuO4 chromophore is suggested.