Syntheses, structures and properties of homo- and heterobimetallic complexes of the type [Zn(tren)NCS]2[M(NCS)4] [tren = tris(2-aminoethyl)amine; M = Zn, Cu]

A 2:2:1:6 molar ratio of Zn(ClO4)2·6H2O, tris(2-aminoethyl)amine (tren), Zn(ClO4)2·6H2O/Cu(ClO4)2·6H2O and NH4NCS in methanol–water solution mixtures affords homo-/heterobimetallic compounds of the type [Zn(tren)NCS]2[M(NCS)4] (M = Zn, 1; M = Cu, 2) which have been characterized using microanalytical, spectroscopic, magnetic and other physicochemical results. The structures of the compounds are determined by X-ray diffraction measurements. Structural analyses reveal that 1 and 2 are isomorphous and consist of two discrete [Zn(tren)NCS]+ cations and a [M(NCS)4]2− (M = Zn/Cu) anion. Zinc(II) centers in the [Zn(tren)NCS]+ units adopt distorted trigonal bipyramidal geometry with ZnN5 chromophores coordinated through four N atoms of tren and one N atom of terminal thiocyanate. Each metal(II) center in [M(NCS)4]2− has a distorted tetrahedral coordination environment with an MN4 chromophore ligated by four N atoms of the terminal thiocyanates. In solid state, doubly N–H…S hydrogen bonded 1D chains of [Zn(tren)NCS]+ cations are interconnected by tetrahedral [Zn(NCS)4]2−/[Cu(NCS)4]2− anions through cooperative N–H…S and N–H…N (in 1) and N–H…S and C–H…S (in 2) hydrogen bonds resulting in 3D network structures. Establishment of such networks seems to be aiding the crystallization.