title: Mechanism of Magnetostructural Transitions in Copper-Nitroxide-Based Switchable Molecular Magnets: Insights from ab Initio Quantum Chemistry Calculations.
abstract: The gradual magnetostructural transition in breathing crystals based on copper(II) and pyrazolyl-substituted nitronyl nitroxides has been analyzed by means of DDCI quantum chemistry calculations. The magnetic coupling constants (J) within the spin triads of Cu(hfac)2L(Bu)·0.5C8H18 have been evaluated for the X-ray structures reported at different temperatures. The coupling is strongly antiferromagnetic at low temperature and becomes ferromagnetic when the temperature increases. The intercluster magnetic coupling (J') is antiferromagnetic and shows a marked dependence on temperature. The magnetostructural transition can be reproduced using the calculated J values for each structure in the simulation of the magnetic susceptibility. However, the μ(T) curve can be improved nicely by considering the coexistence of two phases in the transition region, whose ratio varies with temperature corresponding to both the weakly and strongly coupled spin states. These results complement a recent VT-FTIR study on the parent Cu(hfac)2L(Pr) compound with a gradual magnetostructural transition.
authors.affiliation: †Departamento de Química Física, Universidad de Sevilla, Sevilla, Spain.|‡Institut des Sciences Chimiques de Rennes, UMR 6226 CNRS, Université de Rennes 1, 263 Avenue du Général Leclerc, 35042 Cedex Rennes, France.
authors.forename: Julie
authors.initials: J
authors.lastname: Jung
authors.affiliation: ‡Institut des Sciences Chimiques de Rennes, UMR 6226 CNRS, Université de Rennes 1, 263 Avenue du Général Leclerc, 35042 Cedex Rennes, France.
authors.forename: Boris Le
authors.initials: BL
authors.lastname: Guennic
authors.affiliation: §International Tomography Center, Siberian Branch of Russian Academy of Science and Novosibirsk State University, 630090 Novosibirsk, Russia.
authors.forename: Matvey V
authors.initials: MV
authors.lastname: Fedin
authors.affiliation: §International Tomography Center, Siberian Branch of Russian Academy of Science and Novosibirsk State University, 630090 Novosibirsk, Russia.
authors.forename: Victor I
authors.initials: VI
authors.lastname: Ovcharenko
authors.affiliation: †Departamento de Química Física, Universidad de Sevilla, Sevilla, Spain.
authors.forename: Carmen J
authors.initials: CJ
authors.lastname: Calzado