Tris(ethylenediamine)nickel(II) thio-hydroxogermanate monohydrate: Synthesis, crystal structure, ¹H NMR, EPR, optical and magnetic properties

A new tris(ethylenediamine)nickel(II) complex [Ni(en)₃]GeS₂(OH)₂·H₂O containing a zero-dimensional thiohydroxogermanate [GeS₂(OH)₂]²⁻ anion was synthesized using a solvothermal reaction. The compound crystallizes in monoclinic space group P2₁/n with cell parameters a = 8.676(3) Å, b = 13.574(4) Å, c = 13.976(4) Å and β = 92.67(2)°. The ethylenediamine (en) ligands are bidentate to the Ni²⁺ through the N atoms of the amine group resulting in a distorted octahedral environment around the transition metal. The solid-state ¹H NMR shows four broad singlets attributed to the –CH₂ and –NH₂ protons of the (en) in addition to H₂O and –OH protons. The EPR results indicate that the octahedrally coordinated Ni²⁺ cations are paramagnetic with two unpaired electrons. In agreement with the EPR results, the ZFC/FC magnetization measurements show a paramagnetic response. The title compound is a wide bandgap semiconductor (3.9 eV) and exhibits photoluminescence emission at 488 nm upon excitation (325 nm).