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.
ASJC Scopus subject areas