Anisotropic magnetic interactions in transition metal clusters

NICOLÁS I. NEUMAN; ANA LAURA PÉREZ; ALBERTO C. RIZZI; CARLOS D. BRONDINO

Santa Fe

Workshop; III Taller de Resonancia Magnética. NMR and EPR at the Forefront of Research; 2016

Departamento de Física - Facultad de Bioquímica y Cs. Biológicas - Universidad Nacional del Litoral

CO6: ANISOTROPIC MAGNETIC INTERACTIONS IN TRANSITION METALCLUSTERSNicolás I. Neuman, Ana Laura Pérez, Alberto C. Rizzi and Carlos D. BrondinoDepartamento de Física, FBCB, UNL - CONICET, Santa Fe, Argentinaniconeuman@gmail.comKeywords: Magnetic Interactions, EPR, CobaltMagnetic interactions between transition metal ions are relevant in coordinationchemistry, materials science and biology. (ref) For interacting spin-1/2 centers such asCu(II) extensive theoretical and experimental work has been performed; but for highspin ions such as Co(II) both aspects are less developed. In this work simple formulasare derived for magnetic interactions involving high spin ions that behave as effectiveS´=1/2 centers under experimental conditions. These formulae reduce the number ofunknowns in a pair spin Hamiltonian, thus allowing to more reliably extract structuralinformation, for example from magnetic dipolar interactions. Figure 1 shows asimulation of the energy levels of a S = 3/2 spin pair using a complete spin-Hamiltonianincluding Zeeman, individual zero-field splitting (ZFS) and spin-spin exchange (J) anddipolar (D) interactions (black lines) and the same system using effective S´= 1/2 spins,effective g´-tensors and effective spin-spin interactions (J´ and D´), but no ZFS.Figure 1: Energy levels as a function of the magnetic field for a pair of high spinCo(II) ions treated as real S = 3/2 (black lines) or effective S´ = 1/2 centers (red lines).The obtained formulae are valid for any dimer or cluster containing half-integer highspinions where the individual ZFS is much larger (> 5 times) than the interspinmagnetic interactions, and therefore applicable to most metalloprotein systemscontaining natural or substituted high-spin ions.REFERENCES1. Kahn, O. Molecular Magnetism; VCH Publishers: New York, 1993.2. Bencini, A.; Gatteschi, D. Electron paramagnetic resonance of exchange coupledsystems; Springer: Berlin, 1990.3. Neuman, N. I.; Winkler, E.; Peña, O.; Passeggi, M. C.; Rizzi, A. C.; Brondino, C. D.Inorganic chemistry 2014, 53, 2535.ACKNOWLEDGEMENTSCONICET, ANPCYT