title: Structure, magnetic properties, polarized neutron diffraction, and theoretical study of a copper(II) cubane.
abstract: The paper reports the synthesis, X-ray and neutron diffraction crystal structures, magnetic properties, high field-high frequency EPR (HF-EPR), spin density and theoretical description of the tetranuclear CuII complex [Cu4L4] with cubane-like structure (LH2=1,1,1-trifluoro-7-hydroxy-4-methyl-5-aza-hept-3-en-2-one). The simulation of the magnetic behavior gives a predominant ferromagnetic interaction J1 (+30.5 cm(-1)) and a weak antiferromagnetic interaction J2 (-5.5 cm(-1)), which correspond to short and long Cu-Cu distances, respectively, as evidence from the crystal structure [see formulate in text]. It is in agreement with DFT calculations and with the saturation magnetization value of an S=2 ground spin state. HF-EPR measurements at low temperatures (5 to 30 K) provide evidence for a negative axial zero-field splitting parameter D (-0.25+/-0.01 cm(-1)) plus a small rhombic term E (0.025+/-0.001 cm(-1), E/D = 0.1). The experimental spin distribution from polarized neutron diffraction is mainly located in the basal plane of the CuII ion with a distortion of yz-type for one CuII ion. Delocalization on the ligand (L) is observed but to a smaller extent than expected from DFT calculations.
authors.affiliation: Université Claude Bernard Lyon 1, Laboratoire des Multimatériaux et Interfaces (UMR 5615), Campus de La Doua, 69622 Villeurbanne Cedex (France).
authors.forename: Christophe
authors.initials: C
authors.lastname: Aronica
authors.forename: Yurii
authors.initials: Y
authors.lastname: Chumakov
authors.forename: Erwann
authors.initials: E
authors.lastname: Jeanneau
authors.forename: Dominique
authors.initials: D
authors.lastname: Luneau
authors.forename: Petr
authors.initials: P
authors.lastname: Neugebauer
authors.forename: Anne-Laure
authors.initials: AL
authors.lastname: Barra
authors.forename: Béatrice
authors.initials: B
authors.lastname: Gillon
authors.forename: Antoine
authors.initials: A
authors.lastname: Goujon
authors.forename: Alain
authors.initials: A
authors.lastname: Cousson
authors.forename: Javier
authors.initials: J
authors.lastname: Tercero
authors.forename: Eliseo
authors.initials: E
authors.lastname: Ruiz