Department of Inorganic Chemistry, Kazan State Technological University, 68 K. Marx Street, 420015 Kazan, Russia.
Inorg Chem. 2011 Mar 7;50(5):1905-13. doi: 10.1021/ic102387x. Epub 2011 Jan 27.
Spin crossover in a series of six cyanide-bridged iron(II) tetranuclear square complexes was analyzed using density functional theory (DFT) methods. As the spin crossover between the low-spin (LS) and high-spin (HS) states can occur only for two of four iron ions, we characterized energetically and structurally the [LS-LS], [HS-LS], and [HS-HS] spin-state isomers. For all studied complexes, the energy of the mixed [HS-LS] spin state does not deviate essentially from the halfway point between the energies of homogeneous spin states, thereby satisfying the conditions for an one-step transition between the [LS-LS] and [HS-HS]. This fact reflects the weak elastic coupling between the environments of transiting centers. The two-step spin transition observed in one complex can appear only due to the crystal packing effects. We also evaluated the strength of exchange coupling between the paramagnetic ions in the [HS-HS] state.
使用密度泛函理论（DFT）方法分析了一系列氰桥接的铁（II）四核四方配合物中的自旋交叉。由于自旋交叉只能在四个铁离子中的两个之间发生，因此我们从能量和结构上对[LS-LS]、[HS-LS]和[HS-HS]自旋态异构体进行了表征。对于所有研究的配合物，混合[HS-LS]自旋态的能量基本上不偏离于均匀自旋态之间的能量中点，从而满足了[LS-LS]和[HS-HS]之间的一步转变的条件。这一事实反映了过渡中心环境之间的弱弹性耦合。在一个配合物中观察到的两步自旋转变只能归因于晶体堆积效应。我们还评估了[HS-HS]状态下的顺磁离子之间的交换耦合强度。
