Synthesis, structure, and characterization of a mixed amines thiogermanate [NH4]2[NH2(C)2]2Ge2S6

Abstract A mixed amines thiogermanate, namely (NH4)2[NH2(CH3)2]2Ge2S6 has been successfully synthesized by solvothermal reaction. Single crystal X-ray diffraction indicates the compound crystallizes in monoclinic space group P21/c with the lattice parameters: a = 6.9647(14) A, b = 15.719(3) A, c = 7.2042(14) A, β = 92.76(3)°. The structure features a zero-dimensional [Ge2S6]4− anions which are separated by NH4+ and [NH2(CH3)2]+. Hydrogen bond interactions play a crucial role in its structure formation. X-ray powder diffraction and TG-DSC measurements were performed to study its phase purity and thermal stability. UV–Vis diffuse reflectance spectroscopy coupled with Urbach fitting indicates an indirect optical transition semiconductor with a bandgap value of 3.50 eV. The result of first-principles electronic structure calculation supported the experimental indirect optical transition but the value was under estimated as 3.061 eV. Density of states and population analysis were also calculated to reveal the origin of the bandgap and bond interaction for its structure formation.