title: Prussian blue analogue CsFe[Cr(CN)(6)] as a matrix for the Fe(II) spin-crossover.
abstract: The origin of the intriguing spin-transition behavior of the Prussian blue analogue cesium iron hexacyanochromate CsFe[Cr(CN)6] has been investigated by means of correlated ab initio CASPT2 calculations. Using the smallest transiting core [Fe(NC)6]4-, the relative importance of the local ligand field and the Madelung field generated by the rest of the crystal was estimated. It is shown that in the presence of a frozen-charge environment, the high-spin state lies lower in energy than the low-spin state, thus excluding the possibility of observing a spin transition. In contrast, the charge reorganization in the environment evaluated from unrestricted periodic Hartree-Fock calculations creates a prerequisite for the spin-transition phenomenon. The influence of the disorder in the cesium ions' positions on the spin transition has been examined as a possible stabilizing factor of the low-spin state of [Fe(NC)6]4-. It is concluded that this experimentally observed disorder cannot account solely for the unprecedented behavior of the CsFe[Cr(CN)6] compound.
authors.affiliation: Ecole Normale Supérieure de Lyon, Laboratoire de Chimie, UMR 5182, 46 allée d'Italie, F-69364, Lyon, France.
authors.forename: Boris
authors.initials: B
authors.lastname: Le Guennic
authors.forename: Serguei
authors.initials: S
authors.lastname: Borshch
authors.forename: Vincent
authors.initials: V
authors.lastname: Robert