Investigation on crystal structure, magnetic and near-infrared absorption properties of a novel heteroleptic nickel-bis-1,2-dithiolene compound

A new heteroleptic nickel-bis-1,2-dithiolene ion-pair complex, (4-ClBz-1-APy)[Ni(dmit)(mnt)] (1) (where 4-ClBz-1-APy⁺ = p-chloro-benzyliden-1-aminopyridinium; dmit²⁻ = 2-thioxo-1, 3-dithiole-4, 5-dithiolate; mnt²⁻ = maleonitriledithiolate) was synthesized and characterized structurally. The IR spectra, thermal analysis, magnetic and near-IR absorption properties have been investigated for 1. Complex 1 crystallized in monoclinic system with space group P2₁. The anions and cations form the mixed stacked columns separated by the cation columns. The anion stacks are irregular, in which two neighboring heteroleptic [Ni(dmit)(mnt)]⁻ anions are separated by one 4-ClBz-1-APy⁺ cation. The neighboring anions are connected via lateral-to-lateral S…S contacts of dmit²⁻ ligands and short H…N, H…S and C…S contacts are observed between the cations and the anions. Magnetic susceptibility measurement shows that the magnetic data follows the S = ¹/₂ Heisenberg alternating linear-chain model in the temperature range 40–300 K and Curie-Weiss law below 40 K for 1. Salts 1 exhibits a intense near-IR absorption in the region of 900–1400 nm, and this near-IR absorption feature makes it to be a promising optical material.