Slow magnetic relaxation and proton conduction in a highly hydrogen-bonded dinuclear holmium(III) complex

Abstract

Multifunctional magnetic-electrical materials are highly interesting, such as proton-conductive lanthanide single-ion magnets (SIMs). Herein, we reported the synthesis, crystal structure, magnetic and electrical properties of a bifunctional binuclear holmium(III) complex, [Ho2(H2dobdc)(H2O)14]·(H2dobdc)2·8H2O (Ho2, H4dobdc = 2,5-dioxodo-1,4-benzenedicarboxylate), which was constructed by a hydroxy‑functionalizd dicarboxybenzene and holmium(III) ions. Interestingly, single-crystal X-ray diffraction analysis reveals a highly hydrogen-bonded supramolecular structure and highly oxygenated site were formed within the complex. Magnetic measurements indicate the complex exhibits filed-induced slow magnetic relaxation property. Additionally, the impedance spectroscopy measurements show the complex also exhibits humidity- and temperature-dependent proton conduction behaviour via the Grotthus mechanism. These results support a proton-conductive holmium(III) single-ion magnet of Ho2. This work not only provides the first bifunctional HoIII complexes showing slow magnetic relaxation and proton-conducting behaviour but also a supramolecular way for advanced magnetic-electrical systems linking slow magnetic relaxation with unique proton conducting behaviour exploiting a possible cooperative behaviour.