title: Does the Sign of the Cu-Gd Magnetic Interaction Depend on the Number of Atoms in the Bridge?
abstract: Several theoretical investigations with CASSCF methods confirm that the magnetic behavior of Cu-Gd complexes can only be reproduced if the 5d Gd orbitals are included in the active space. These orbitals, expected to be unoccupied, do present a low spin density, which is mainly due to a spin polarization effect. This theory is strengthened by the experimental results reported herein. We demonstrate that Cu-Gd complexes characterized by Cu-Gd interactions through single-oxygen and three-atom bridges consisting of oxygen, carbon, and nitrogen atoms, present weak ferromagnetic exchange interactions, whereas complexes with bridges made of two atoms, such as the nitrogen-oxygen oximato bridge, are subject to weak antiferromagnetic exchange interactions. Therefore, a bridge with an odd number of atoms induces a weak ferromagnetic exchange interaction, whereas a bridge with an even number of atoms supports a weak antiferromagnetic exchange interaction, as observed in pure organic compounds and also, as in this case, in metal-organic compounds with an active spin polarization effect.
authors.affiliation: Laboratoire de Chimie de Coordination du CNRS, 205, route de Narbonne, BP 44099, 31077, Toulouse Cedex 4, France. jean-pierre.costes@lcc-toulouse.fr.|Université de Toulouse; UPS, INPT, 31077, Toulouse Cedex 4, France. jean-pierre.costes@lcc-toulouse.fr.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Costes
authors.affiliation: Laboratoire de Chimie de Coordination du CNRS, 205, route de Narbonne, BP 44099, 31077, Toulouse Cedex 4, France.|Université de Toulouse; UPS, INPT, 31077, Toulouse Cedex 4, France.
authors.forename: Carine
authors.initials: C
authors.lastname: Duhayon
authors.affiliation: Laboratoire de Chimie de Coordination du CNRS, 205, route de Narbonne, BP 44099, 31077, Toulouse Cedex 4, France.|Université de Toulouse; UPS, INPT, 31077, Toulouse Cedex 4, France.
authors.forename: Sonia
authors.initials: S
authors.lastname: Mallet-Ladeira
authors.affiliation: Laboratoire de Chimie de Coordination du CNRS, 205, route de Narbonne, BP 44099, 31077, Toulouse Cedex 4, France.|Université de Toulouse; UPS, INPT, 31077, Toulouse Cedex 4, France.|Department of Chemistry, Moldova State University, A. Mateevici Str. 60, 2009, Chisinau, Moldova.
authors.forename: Sergiu
authors.initials: S
authors.lastname: Shova
authors.affiliation: Laboratoire de Chimie de Coordination du CNRS, 205, route de Narbonne, BP 44099, 31077, Toulouse Cedex 4, France.|Université de Toulouse; UPS, INPT, 31077, Toulouse Cedex 4, France.
authors.forename: Laure
authors.initials: L
authors.lastname: Vendier
keywords: Cu-Gd complexes; coordination chemistry; magnetic properties; spin polarization; structure elucidation