Le Guennic Boris, Borshch Serguei, Robert Vincent
Ecole Normale Supérieure de Lyon, Laboratoire de Chimie, UMR 5182, 46 allée d'Italie, F-69364, Lyon, France.
Inorg Chem. 2007 Dec 24;46(26):11106-11. doi: 10.1021/ic701352c. Epub 2007 Nov 23.
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.
通过相关的从头算耦合簇单双激发组态相互作用（CASPT2）计算，对普鲁士蓝类似物六氰合铬酸铯铁（CsFe[Cr(CN)₆]）引人入胜的自旋转变行为的起源进行了研究。使用最小的过渡核心[Fe(NC)₆]⁴⁻，估算了局部配体场和晶体其余部分产生的马德隆场的相对重要性。结果表明，在电荷冻结环境中，高自旋态的能量低于低自旋态，因此排除了观察到自旋转变的可能性。相反，通过无限制周期哈特里-福克计算评估的环境中的电荷重组为自旋转变现象创造了前提条件。研究了铯离子位置的无序对自旋转变的影响，将其作为[Fe(NC)₆]⁴⁻低自旋态的一种可能的稳定因素。得出的结论是，这种实验观察到的无序不能单独解释CsFe[Cr(CN)₆]化合物前所未有的行为。
