RESUMO
Two new pi-conjugated 1,3-dithiol-2-ylidene-containing ligands, 4,5-[1',4']dithiino[2',3'-b]quinoxaline-2-bis(2-pyridyl)methylene-1,3-dithiole (L(1)) and 4,5-bis(methylthio)-2-bis(2-pyridyl)methylene-1,3-dithiole (L(2)), have been synthesized and characterized. Using L(1), L(2), or dimethyl 2-[di(pyridin-2-yl)methylene]-1,3-dithiole-4,5-dicarboxylate (L(3)) as the auxiliary ligand and [(Tp)Fe(CN)(3)](-) or [(i-BuTp)Fe(CN)(3)](-) [Tp = tris(pyrazolyl)borate; i-BuTp = 2-methylpropyltris(pyrazolyl)borate] as the building block, two rectangular-square Fe(2)Ni(2) clusters [(Tp)Fe(CN)(3)Ni(L(1))(2)](2).2ClO(4).6H(2)O (1) and [(i-BuTp)Fe(CN)(3)Ni(L(3))(2)](2).2ClO(4).6H(2)O (2) and two trinuclear clusters [(Tp)(2)Fe(2)(CN)(6)Ni(L(2))(2)].8H(2)O (3) and [(Tp)(2)Fe(2)(CN)(6)Co(L(3))(2)].5H(2)O (4) have been prepared in parallel and structurally characterized. Complexes 1 and 2 show similar square structures, and weaker intermolecular pi-pi-stacking interactions through the pyrazolyl groups of the Tp(-) ligands are observed. 2D sheet structures are formed in complexes 3 and 4 through intermolecular pi-pi-stacking interactions. In 3, shorter S...S contacts further connect the 2D sheets to 3D supramolecular structures. Magnetic studies show intramolecular ferromagnetic coupling in complexes 1-4. Complexes 1 and 2 show obvious frequency dependencies in the alternating-current magnetic susceptibility data, indicating single-molecule-magnet behavior with effective spin-reversal barriers of 8.7 K for 1 and 13.5 K for 2, respectively.