Proton Conductive Mononuclear Hydrogen-Bonded Cobalt(II) Spin Crossover Complex

The development of molecule-based switchable multifunctional materials remains an important challenge in molecular science. In particular, achieving high proton conductivities spin crossover (SCO) compounds is significant interest as the state can be controlled via transfer induced by electric field, which leads to magnetoelectric effects and spintronics. However, best our knowledge, no studies have reported on proton-conductive SCO complexes. Thus, herein, we demonstrated conductivity a mononuclear hydrogen-bonded Co(II) compound, [Co(COOH-terpy)2](ClO4)2·4H2O (1·4H2O; COOH-terpy = 4′-carboxyl-2,2′:6′,2″-terpyridine). [Co(COOH-terpy)2] 2+ cation assembled solid hydrogen-bonding between lattice water molecules formed 1D chain. Each chain was linked CH−π interactions C–C produced complicated 3D supramolecular framework. Magnetic susceptibility alternative current impedance measurements for 1·4H2O revealed incomplete transition behaviors high-proton-conduction identical temperature regions. exhibited 1.68 × 10–3 S cm–1 at 353 K 98% relative humidity. Notably, this first example compound having networks. results study used develop new design guidelines conductors, further leading switching materials.