Four new chalcohalides, NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br and CsBa2SnS4Cl: Syntheses, crystal structures and optical properties

A new series of chalcohalides, NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br and CsBa2SnS4Cl have been obtained. They present three different space groups: NaBa2SnS4Cl and KBa2SnS4Cl in space group I4/mcm, KBa2SnS4Br in Pnma and CsBa2SnS4Cl in space group P21/c. UV-vis-NIR spectroscopy measurements indicate that NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br and CsBa2SnS4Cl have band gaps of 2.28, 2.30 1.95, and 2.06 eV, respectively. 174