A proton conductor showing an indication of single-ion magnet behavior based on a mononuclear Dy(iii) complex

Abstract

Crystalline molecular materials exhibiting both proton conduction and single-molecule magnet (SMM) behavior would offer great opportunities for applications in fuel cell, molecular spintronic, and high-density data storage technologies. However, such kinds of materials have rarely been reported. Herein, the first example of a mononuclear proton-conductive Dy^III-SMM, namely [Dy(H₂bim)₂(H₂O)₂(NO₃)₂](NO₃) (1) (H₂bim = 2,2′-biimidazole), was synthesized and characterized. Complex 1 displays high proton conductivity (σ) of 1.16 × 10⁻³ S cm⁻¹ at 35 °C and 100% relative humidity (RH). The 1D H-bonding network, with 2,2′-biimidazole and coordinated water molecules acting as H-bonding donors and nitrate anions (NO₃⁻) acting as H-bonding acceptors, plays a dominant role in allowing this high conductivity. Magnetic studies indicated that complex 1 exhibits single-ion magnet behavior.