Solid‐State Hydrogen‐Bond Alterations in a [Co2Fe2] Complex with Bifunctional Hydrogen‐Bonding Donors
Abstract
A hydrogen‐bonding donor–acceptor system, [Co2Fe2(bpy*)4(CN)6(tp*)2](PF6)2⋅2ABA⋅4BN⋅2PE (1 solv), was prepared by co‐crystallization of an external stimuli‐responsive cyanide‐bridged tetranuclear [Co2Fe2] complex and bifunctional hydrogen‐bonding donors, p‐aminobenzoic acid. Compound 1 solv exhibited a gradual electron‐transfer‐coupled spin transition (ETCST), and the removal of solvent molecules led to an abrupt thermal ETCST behavior with increased transition temperature. X‐ray structural analysis revealed that the modification of ETCST was caused by a significant alteration of a hydrogen‐bonding mode between the tetranuclear [Co2Fe2]2+ cations and ABA molecules. Variable temperature IR measurements indicated that the desolvated form, 1 desolv, showed dynamic alteration of hydrogen‐bonding interactions coupled with thermal ETCST behavior. These results suggested that the tetranuclear [Co2Fe2] complex shows solid‐state modulations of hydrogen‐bond strengths by external stimuli.
