Molecular Structure and Single Crystal EPR Spectra of Bis (L-valinato)copper(II) Monohydrate, Cu[H2NCHCO2CH(CH3)2].H2O

C. A. STEREN; R. CALVO; E. E. CASTELLANO; S. M. FABIANE; O. E. PIRO

PHYSICA B - CONDENSED MATTER

Elsevier

Año: 1990 vol. 164 p. 323 - 330

0921-4526

A magnetic-structural study of the title compound, Cu(L-Val)2. H,O, employing EPR spectroscopy and X-ray diffraction methods is presented. The complex crystallizes in the space group C2 with a = 21.314(5) A, b = 9.586(2) A, c = 7.417(2) A, /3 = 108.89(2) °. and Z = 4. The Cu(ll) ions, which are in a five-fold pyramidal coordination, with two valine molecules and a water oxygen (Ow) are arranged in layers parallel to (100). Neighboring Cu(L-val)2•H,O molecules in a layer are linked to each other by a net of Ow-H- - - O and N-H--- O hydrogen bonds. The single EPR line observed arises from the collapse of the resonances due to the two magnetically inequivalent Cu(ll) ions in the lattice caused by the exchange interaction. The obtained g|| =2.254(1) and g(perp) = 2.061(1) principal values of the molecular gyromagnetic tensor point to a d(x2 - y2) orbital for the unpaired electron. The orientation of this orbital was also obtained from our EPR data. The angular variation of the resonance line width has contributions arising from the dipolar interaction modulated by exchange effects in a two-dimensional magnetic lattice, and from the incomplete collapse of the hyperfine structure. The EPR results are compared to those obtained in other copper amino acid complexes.