Hydrothermal growth of single crystals of TMA-CuGS-2, [C₄H₁₂N]₆[(Cu_0.44Ge _0.56S_2.23)₄(Ge₄S₈) ₃] and their characterization using synchrotron/imaging plate data

Single crystals of TMA-CuGS-2, [C₄H₁₂N]₆[(Cu_0.44Ge _0.56S_2.23)₄(Ge₄S₈) ₃], were synthesized hydrothermally, and the structure was determined using data collected from sealed-tube and synchrotron X-ray sources. This compound consists of Ge₄S₁₀^4- adamantine clusters, corner-sharing with MS_x units (M = Cu, Ge; x = 3 or 4), forming an open framework with tetramethylammonium cations residing within four intersecting channels. Disorder in the M sites causes the composition of the framework to deviate from the ideal stoichiometry, Ge_0.71M_0.24S₂, realized when M = Cu and x = 4. This is consistent with results obtained from electron-probe microanalysis. The structure refinements were carried out in space group I43d with cell parameter a = 20.629 (1) Å. Fourteen unique weak reflections of the type hhl, 2h + l = 4n + 2, forbidden in I43d, were detected only in the synchrotron/imaging plate experiment. Trial refinements in space groups R3 and I2₁3 suggest their origin in either weak ordering or multiple scattering effects.