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

•Synthesis of [Ni(en)3]GeS2(OH)2·H2O by mild solvothermal route.•Structural investigation utilizing X-ray diffraction, 1H NMR and EPR spectroscopy.•Magnetization measurements revealing the paramagnetic character.•Optical spectroscopic studies determining the bandgap energy and the PL emission.