Peculiarities of crystal structures and magnetic properties of Cu(II) and Ni(II) mixed-ligand complexes on the 1,3-dithiole-2-thione-4,5-dithiolate basis

Mixed-ligand Cu(II) and Ni(II) complexes, [Cu(dmit)(bpy)] 2 ( I), [Ni(dmit)(phen) 2] ( II) and [Ni(dmit)(phen) 2]·CH 2Cl 2 ( III) (dmit=1.3-dithiole-2-thione-4.5-dithiolate, phen=1.10-phenantroline, bpy=2.2′-bipyridine) have been prepared by ligand exchange between phen or bpy and (Bu 4N) 2[M(dmit) 2] (M=Ni, Cu) and characterized by elemental analysis, IR spectroscopy, single-crystal X-ray analysis and by investigation of magnetic and resonance properties. In complex I, the monomeric units form dimers in a head-to-tail arrangement by weak coordination bonds between copper and dithiolate sulfur atoms and π–π interactions between dmit and bpy from neighboring monomers. Dimers in I are further extended into chains by weak Cu–S(thione) contacts. In crystal packing of complex II and III, there exists a weak π–π interaction between two parallel phen molecules of the adjacent complexes. As a consequence, the magnetic and resonance characteristics of copper complex may be described in approximation of exchange-coupled pairs of Cu 2+ ions with ion spin S=1/2. The nickel complexes are described by isotropic exchange model for single-site spin S=1. π–π (- - -) and C–H···π ( ▪) – interactions in complex [Ni(dmit)(phen) 2]. [Display omitted] ► Mixed-ligand Cu(II) and Ni(II) complexes. ► Cu(II) complex forms dimers in a head-to-tail arrangement. ► The dimerization leads to an indirect antiferromagnetic exchange interaction. ► A weak π–π interaction exists in Ni(II) complexes. ► Large inter-ion distances lead to two- or three-dimensional character of indirect exchange interactions of Ni 2+ ions.