Synthesis and Characterization of Cs4Ga6Q11 (Q = S, Se): Chalcogenometalates with Exotic Polymeric Anions

Two new chalcogenogallates Cs(4)Ga(6)Q(11) (Q = S, Se) were obtained by a controlled thermal treatment of CsN3 in the presence of stoichiometric amounts of Ga(2)Q(3) and the elemental chalcogens at elevates temperatures. Both isotypic compounds crystallize in the space group P (1) over bar (no. 2). The most prominent structural feature in these chalcogenogallates are the complex anionic Dreier double chains (1)(infinity)[Ga(6)Q(11)(4-)] formed by condensed GaQ(4) tetrahedra. The semiconductors Cs4Ga6S11 (E-g = 3.14 eV) and Cs4Ga6Se11 (E-g = 2.41 eV) were further studied by using UV/Vis, Cs-133 and Ga-71 solid-state NMR spectroscopy, and complementary DFT calculations. The Cs-133 MAS NMR spectra are characteristic for cationic cesium and vibrational spectra show two distinct regions, attributed to the Ga-Q valence and deformation vibrations, respectively. High-temperature studies revealed incongruent melting of both solids, which is also depicted in updated binary phase-diagrams Cs(2)Q-Ga(2)Q(3) (Q = S, Se).