Electronic and Structural Order Parameters in Mn3+ Metal-Organics with S=1 to S=2 Spin State Switching
Grace Morgan, Irina Kühne, Anthony J. Fitzpatrick, Brendan Gildea, and Helge Müller-Bunz
School of Chemistry, University College Dublin, Belfield, Dublin 4, Ireland
grace.morgan@ucd.ie
Spin crossover (SCO)1 complexes are molecular switches where the arrangement of electrons in d-orbitals can be reversibly manipulated from paired to unpaired by input of thermal energy, pressure, magnetic field or irradiation. SCO occurs within a single molecule, and rearranging the electrons produces a new electronic state with a different size and shape. While the LS HS size difference is regularly factored into theoretical treatments of how electron-phonon coupling2 and elastic interactions3 affect SCO profile, significant differences in molecular shape between the two states are not included in these models. The recent surge in reports of multistep and, in some cases, incomplete SCO which is accompanied by a crystallographic phase transition includes several examples where there is also a change in point group symmetry at the spin-active molecule. We are interested to further investigate the relationship between the conformational changes which may accompany the S = 1 to S = 2 spin state change at the molecular level in Mn3+ SCO complexes in the solid state and in solution, and the effect on the structural order parameter and on the magnetic anisotropy.
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