Mapping the cooperativity pathways in spin crossover complexes |
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Authors: | Matthew G. Reeves Elodie Tailleur Peter A. Wood Mathieu Marchivie Guillaume Chastanet Philippe Guionneau Simon Parsons |
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Affiliation: | Centre for Science at Extreme Conditions, EaStCHEM School of Chemistry, The University of Edinburgh, King''s Buildings, West Mains Road, Edinburgh Scotland EH9 3FJ UK.; CNRS, Univ. Bordeaux, Bordeaux INP, ICMCB, UMR 5026, 87 av. Dr A. Schweitzer, F-33600 Pessac France.; Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge England CB2 1EZ UK, |
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Abstract: | Crystal packing energy calculations are applied to the [Fe(PM-L)2(NCS)2] family of spin crossover (SCO) complexes (PM-L = 4-substituted derivatives of the N-(2-pyridylmethylene)-4-aminobiphenyl ligand) with the aim of relating quantitatively the cooperativity of observed SCO transitions to intermolecular interactions in the crystal structures. This approach reveals a linear variation of the transition abruptness with the sum of the magnitudes of the interaction energy changes within the first molecular coordination sphere in the crystal structure. Abrupt transitions are associated with the presence of significant stabilising and destabilising changes in intermolecular interaction energies. While the numerical trend established for the PM-L family does not directly extend to other classes of SCO complex in which the intermolecular interactions may be very different, a plot of transition abruptness against the range of interaction energy changes normalised by the largest change shows a clustering of complexes with similar transition abruptness. The changes in intermolecular interactions are conveniently visualised using energy difference frameworks, which illustrate the cooperativity pathways of an SCO transition.The abruptness of spin crossover (SCO) is related to intermolecular energy changes occurring over the course of an SCO transition. Crossover is abrupt when SCO-induced strain is accommodated synergistically in a few key interactions. |
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