| Abstract
| - Solvent exchange caused reversible variations in color, magnetic properties, and the Faradayspectra of CoII1.5[CrIII(CN)6]·7.5H2O (1) prepared in water. Compound 1 turned from peach to deep blue,which was due to a change in the coordination geometry on CoII ion from six-coordinate pseudo-octahedral(OhCoII) to four-coordinate pseudo-tetrahedral (TdCoII) geometries, when it was immersed in EtOH. Theconfirmed formula for the deep blue powder was CoII1.5[CrIII(CN)6]·2.5H2O·2.0EtOH. The magnetic propertiesalso changed; that is, the magnetic critical temperature, saturation magnetization, and coercive field wentfrom 25 to 18 K, from 7.0 to 5.5 μB, and from 240 to 120 G, respectively. This solvatomagnetism is becausethe ferromagnetic magnetic coupling between OhCoII (S = 3/2) and CrIII (S = 3/2) is replaced by theantiferromagnetic coupling between TdCoII (S = 3/2) and CrIII (S = 3/2). Accompanying the solvatochromismand solvatomagnetism, the Faraday spectra drastically changed. The Faraday ellipticity (FE) spectrum of1 had a distorted dispersive peak (A), which is due to the 4T1g → 4T1g, 2T1g transitions of OhCoII ion, around480 nm, but the FE spectra of 2 showed a new dispersive-shaped band (B) at 580 nm. The observed Bband was assigned to the 4A2 → 4T2 transition of the TdCoII ion. The Faraday spectra were well reproducedby a simulation that considers the ligand field splitting, spin−orbital coupling, and the ferromagnetic ordering.These solvatochromic effects were repeatedly observed.
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