Observation of an unusual hysteretic magnetic transition in a heteroleptic nickel-bis-1,2-dithiolene compound

A heteroleptic nickel-bis-1,2-dithiolene ion–pair complex, [BzQl][Ni(dmit)(mnt)] (where BzQl+ = 1-(benzyl)quinolinium; dmit2− = 2-thioxo-1,3-dithiole-4,5-dithiolate, mnt2− = maleonitriledithiolate), was synthesized and characterized structurally, which exhibited novel magnetic bistability. The compound crystallized in triclinic system with space group P-1. The anions and cations form alternating layered alignments, and the anionic layer is built by the irregularly heteroleptic [Ni(dmit)(mnt)]− chains, where the neighboring anions are connected via lateral-to-lateral S…S contacts of dmit2− ligands. The temperature dependences of magnetic susceptibility follow the S = ½ Heisenberg alternating linear-chain model in high-temperature phase and Curie–Weiss law in low-temperature phase.