A Mixed-Valence {Fe13 } Cluster Exhibiting Metal-to-Metal Charge-Transfer-Switched Spin Crossover.

It is promising and challenging to manipulate the electronic structures and functions of materials utilizing both metal-to-metal charge transfer (MMCT) and spin-crossover (SCO) to tune the valence and spin states of metal ions. Herein, a metallocyanate building block is used to link with a FeII -triazole moiety and generates a mixed-valence complex {[(Tp4-Me )FeIII (CN)3 ]9 [FeII 4 (trz-ph)6 ]}⋅[Ph3 PMe]2 ⋅[(Tp4-Me )FeIII (CN)3 ] (1; trz-ph=4-phenyl-4H-1,2,4-triazole). Moreover, MMCT occurs between FeIII and one of the FeII sites after heat treatment, resulting in the generation of a new phase, {[(Tp4-Me )FeII (CN)3 ][(Tp4-Me )FeIII (CN)3 ]8 [FeIII FeII 3 (trz-ph)6 ]}⋅ [Ph3 PMe]2 ⋅[(Tp4-Me )FeIII (CN)3 ] (1 a). Structural and magnetic studies reveal that MMCT can tune the two-step SCO behavior of 1 into one-step SCO behavior of 1 a. Our work demonstrates that the integration of MMCT and SCO can provide a new alternative for manipulating functional spin-transition materials with accessible multi-electronic states.