Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland.
Inorg Chem. 2010 Mar 15;49(6):2765-72. doi: 10.1021/ic901985z.
In this paper we report the synthesis and the structural and magnetic properties of the series of ionic compounds with general formula: M(I)[Co(bpy)(3)][Mo(CN)(8)] x nH(2)O (M(I) = Li, n = 8 (1), M(I) = K, n = 8 (2), M(I) = Rb, n = 8 (3), M(I) = Cs, n = 7.5 (4)). Solids 1-4 are characterized by the optical outer-sphere metal-to-metal charge transfer (MMCT) transition from Mo(IV) center to Co(III) center in the visible region and the Co(III)Mo(IV) <==> Co(II)Mo(V) spin equilibrium strongly dominated by the Co(III)Mo(IV) form. We show a gentle thermal treatment of diamagnetic compounds 1-4 leading to the dehydrated forms 1a-4a, which reveal a significant increase of paramagnetic contribution (from 0.5 to 2% to 30-40%). The rehydration allows to recover the diamagnetic phases 1b-4b of compositions and properties similar to those of 1-4. The irradiation of the dehydrated form 2a within the MMCT band in the Superconducting Quantum Interference Device (SQUID) cavity at T = 10 K causes further increase of the Co(II)Mo(V) contribution giving the metastable phase annealed back to the 2a phase after heating above T = 290 K. The IR, electron paramagnetic resonance (EPR), and X-ray photoelectron spectroscopy (XPS) spectroscopic data along with the magnetic data are interpreted in terms of strong modification of the Co(III)Mo(IV) <==> Co(II)Mo(V) equilibrium occurring in these systems.
在本文中，我们报告了一系列离子化合物的合成以及它们的结构和磁性性质，这些化合物的通式为：M(I)[Co(bpy)(3)][Mo(CN)(8)] x nH(2)O（M(I) = Li，n = 8（1），M(I) = K，n = 8（2），M(I) = Rb，n = 8（3），M(I) = Cs，n = 7.5（4））。固态化合物 1-4 的特点是从 Mo(IV)中心到 Co(III)中心的光学外轨金属-金属电荷转移（MMCT）跃迁，在可见区域，Co(III)Mo(IV) <==> Co(II)Mo(V)自旋平衡强烈受到 Co(III)Mo(IV)形式的支配。我们展示了对反磁性化合物 1-4 进行温和热处理，得到脱水形式 1a-4a，这导致顺磁贡献显著增加（从 0.5%到 2%增加到 30-40%）。再水合可以恢复组成和性质与 1-4 相似的反磁性相 1b-4b。在超导量子干涉装置（SQUID）腔中，在 MMCT 带内对脱水形式 2a 进行辐照，在 T = 10 K 时，进一步增加 Co(II)Mo(V)的贡献，得到经过加热后返回 2a 相的亚稳相。IR、电子顺磁共振（EPR）和 X 射线光电子能谱（XPS）光谱数据以及磁性数据，解释了这些系统中 Co(III)Mo(IV) <==> Co(II)Mo(V)平衡发生的强烈变化。
