Transition metal complexes based on pyridine ligand containing both bis(2-pyridyl) and 1,3-dithiole-2-ylidene units: Syntheses, structures, and magnetic studies

摘要

Two new mononuclear spin-crossover iron(II) complexes, [FeL_2(NCS)_2] H_20 (1) and [FeL_2(NCSe)_2] (2), have been synthesized from the reaction of the versatile ligand 4,5-bis(2-cyanoethylthio)-2-bis(2-pyridyl)methylene-1,3-dithiole (L), Fe(ClO_4)_2, and KNCX (X = S/Se). Reactions of L with Cu~(ll) or Co~(ll) salts afford one mononuclear complex [CuL(hfac)_2] _ CH_3OH (hfac = hexafluoroacetylacetonate) (3), one dinuclear complex [(CuLCl)_2(μ-Cl)_2]_ CH_3OH (4), and two 1D chain species, [CuL_2]_n(BF_4)_(2n) (5) and [CoL_2]_n (ClO_4)_(2n) 2nCH_2Cl_2 (6). The crystal structures of complexes 1 and 3-6 have been determined by X-ray crystallography. Short intermolecular S… S contacts between neighboring 1D arrays are observed in 5 and 6, which lead to the formation of the 2D structure. The magnetic properties are studied, and antiferromagnetic couplings between the Cu~(II) centers across the chloride bridges have been found in 4 = 2.04 cm~(-1)). Spin-crossover behaviors between high and low spin states are observed at T_(1/2) = 80 K for 1 and T_(1/2) = 300 K for 2, respectively.