Probing Effective Hamiltonian Operators by Single-Crystal EPR: A Case Study Using Dinuclear Cr(III) Complexes.

Abstract

The use of a simple two-center model to describe exchange-coupled systems of various complexities is common in the field of coordination chemistry and molecular magnetism. In this work we investigate the applicability of this model experimentally, employing multifrequency, single-crystal EPR on axial dinuclear chromium(III) systems amenable to accurate parametrizations. The very high confidence with which zero-field splitting parameters can be determined by this technique, applied to the systems in question, allows for an in-depth analysis of the modeling. We experimentally demonstrate and qualitatively account for the energy-dependent modification of the spin-multiplet anisotropies, which is introduced by the exchange interaction. Even for the simple systems under consideration, we find that the standard modeling provides an inadequate parametrization of experimental data, and we present a convenient model extension, which improves the description.