Rotation of Hexamethylenetetramine Molecules Induces Reversible Electromagnetic Coupling Properties in Isothiocyanato-Nickel Complexes

Multifunctional coupled hybrid materials have extremely high potential for application in a variety of complex scenarios owing to advantages such as versatility and controllable properties. In this study, a novel functional material with electromagnetic coupling properties [Ni(NCS)₄(C₆H₁₃N₄)₂] (<b>1</b>) was obtained by naturally evaporating an aqueous solution of nickel chloride hexahydrate, hexamethylenetetramine (HMTA), and potassium thiocyanate as raw materials. Structure-property characterization revealed that <b>1</b> crystallized in the <i>P</i>2₁/n space group with a two-dimensional (2D) network structure formed by hydrogen-bonding interactions between neighboring nickel complexes. Calculations using the Gaussian program indicated that HMTA exhibited pronounced spatial molecular rotation. This induced obvious reversible dielectric cycling near 240 K, giving rise to semiconducting properties and an optical band gap of 3.35 eV. Molecular rotation caused changes in the 2D network structure, inducing short-range magnetic ordering in the temperature range of 2-50 K. This resulted in the formation of a potential ferromagnet and the presence of a distinct reversible redox peak in the -0.2-0.8 V potential range. Structure-property analyses showed that <b>1</b> is a supramolecular rotation-induced semiconducting multifunctional crystalline material with reversible electromagnetic coupling properties.