Structure, Single Crystal EPR Spectra and Exchange Interactions in [Cu(L-proline)2]2.5H2O and Cu(D,L-proline)2.2H2O

R. P. SARTORIS; L. ORTIGOZA; N. M. C. CASADO; R. CALVO; E. E. CASTELLANO; O. E. PIRO

INORGANIC CHEMISTRY

American Chemical Society

Año: 1999 vol. 38 p. 3598 - 3604

0020-1669

A new copper(II) compound, [Cu(L-proline)2]2â5H2O (C20Cu2H42N4O13) (called compound I) was synthesized and crystallized, and its structure was solved using X-ray methods. It is monoclinic, space group P21, with a = 11.187(1) Å, b = 12.172(3) Å, c = 11.661(1) Å, beta = 114.96(1)°, and Z = 2. There are two chemically different copper molecules (labeled A and B), both with the copper atom in a N2O2 square planar coordination. Molecule type A has one water molecule in an apical position. Molecule B has water molecules in each of the two apical positions. Single-crystal EPR measurements have been performed in I and also in Cu(D,L-proline)2â2H2O (compound II). From the similar angular variations of the position of the single resonance observed in both compounds, we evaluated the molecular g tensors. Interpretation of the molecular g tensors resulted in dx2-y2 orbital ground states. From the angular variations of the line width we calculated the magnitude of the exchange interactions coupling neighbor copper ions in each compound. In I copper ions type A at 7.25 Å are arranged in chains coupled through axial-equatorial bonds. The exchange coupling within these chains is |J/k| = 118 mK. The coupling between copper ions type B is weaker. However, the interactions between copper ions type A and B generate a threedimensional magnetic network. Our data in compound II indicate that a superexchange pathway containing a weak hydrogen bond C-H- - -O is the path for an exchange interaction with |J¢/k| = 48 mK between coppers in neighbor layers at 9.75 Å.