3D structure and spin-gap transition observed in a new Ni(mnt)2-based molecular solid containing substituted 4-dimethylaminopyridinium

A new molecular solid [FClBzPyN(CH3)2][Ni(mnt)2](1) ([FClBzPyN(CH3)2] = [1-(4′-fluoro-2′-chlorobenzyl)-4-dimethylaminopyridinium], mnt = maleonitriledithiolate), has been prepared and characterized by single crystal X-ray diffraction and magnetic measurements. The Ni(III) ions of 1 form a quasi-one-dimensional zigzag magnetic chain within a Ni(mnt)2− column through Ni···S, Ni···Ni, or π···π interactions with Ni···Ni distances of 3.953 and 3.990 Å. The Cl···S short interactions and weak hydrogen bonds between anions and cations in the crystal generate a 3D network structure. Magnetic susceptibility measurements in the temperature range 1.8–300 K show that 1 exhibits a spin-gap transition around 55 K, and antiferromagnetic interaction (θ = −50.8 K) in the high-temperature phase (HT) and spin gap (Δ/kb = 132.6 K) in the low-temperature phase (LT).