title: Structure, Single Crystal EPR Spectra, and Exchange Interactions in [Cu(L-proline)(2)](2).5H(2)O and Cu(D,L-proline)(2).2H(2)O.
abstract: A new copper(II) compound, [Cu(L-proline)(2)](2).5H(2)O (C(20)Cu(2)H(42)N(4)O(13)) (called compound I) was synthesized and crystallized, and its structure was solved using X-ray methods. It is monoclinic, space group P2(1), with a = 11.187(1) Å, b = 12.172(3) Å, c = 11.661(1) Å, beta = 114.96(1) degrees, and Z = 2. There are two chemically different copper molecules (labeled A and B), both with the copper atom in a N(2)O(2) 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)(2).2H(2)O (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 d(x)()()2(-)(y)()()2 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 three-dimensional 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.
authors.affiliation: Departamento de Física, Facultad de Ciencias Exactas, Universidad Nacional de La Plata and Programa PROFIMO (CONICET), C.C. 67, 1900 La Plata, Argentina.
authors.forename: R. P.
authors.initials: RP
authors.lastname: Sartoris
authors.forename: L.
authors.initials: L
authors.lastname: Ortigoza
authors.forename: N. M. C.
authors.initials: NM
authors.lastname: Casado
authors.forename: R.
authors.initials: R
authors.lastname: Calvo
authors.forename: E. E.
authors.initials: EE
authors.lastname: Castellano
authors.forename: O. E.
authors.initials: OE
authors.lastname: Piro