Crystal structures, electronic spectra and magnetic properties of homoleptic and heteroleptic metal-dithiolate molecular solids

Abstract

Two nickel-bis-(1,2-dithiolate) molecular solids, (4-ClBzEt3N)[Ni(dmit)x(mnt)2−x] (x = 0 (1) and 1 (2)) (where 4-ClBzEt3N+ = 4-chloro-benzyltriethylammonium; dmit2− = 2-thioxo-1,3-dithiole-4,5-dithiolate; mnt2− = maleonitriledithiolate) were synthesized and characterized structurally. The infrared (IR) spectra, powder X-ray diffraction (PXRD), UV–Vis absorption and magnetic properties have been investigated for 1 and 2. The homoleptic metal-dithiolene complex 1 crystallizes in monoclinic system with space group P1¯. The anions of 1 are aligned into columnar stacks along a-axis direction. The neighboring anions are connected via lateral-to-lateral S…S contacts of mnt2− ligands are observed between the cations and the anions. The powder X-ray diffraction patterns are in good agreement with the simulated patterns based on the crystal structures, indicating the purity of the as-grow crystals. FT-IR and UV–Vis absorption spectra were recorded and analyzed for 1 and 2. The variable-temperature magnetic susceptibility analysis shows that 1 follow the Curie–Weiss law below 50 K and a spin-gap between 50 and 205 K, and 2 exhibits a weak antiferromagnetic exchange interaction as the temperature is lowered and the magnetic susceptibility data follows the S = 1/2 Heisenberg alternating linear-chain model in the temperature range 109–400 K and a spin gap below 109 K for 2.