[(Ba19Cl4)(Ga6Si12O42S8)]: a Two-Dimensional Wide-Band-Gap Layered Oxysulfide with Mixed-Anion Chemical Bonding and Photocurrent Response.

Mixed-anion compounds play an essential part in modern structural chemistry. In this Communication, an unprecedented hexanary oxysulfide, [(Ba19Cl4)(Ga6Si12O42S8)] (FJ-1), was synthesized at 1073 K by a standard solid-state method, which is a new phase in the AE/MIII/MIV/O/Q/X (AE = alkaline-earth metal; MIII = group 13 metal; MIV = group 14 metal; Q = chalcogen; X = halogen) system. FJ-1 adopts a new structure type and crystallizes in the orthorhombic system with space group Cmcm. In the structure, unique two-dimensional [Ga6Si12O42S8]34- layers formed by the familiar [SiO4] species and unusual heteroligand [GaO2S2] and [GaO3S] tetrahedra extend the intralayer linking. Significantly, a photoelectrochemical test revealed that FJ-1 is photoresponsive under ultraviolet illumination. Moreover, density functional theory calculations were employed to gain insight into the relationship between the electronic structure and optical properties. Such work will be conducive to the structural diversity of gallium coordination chemistry by exploration of the new mixed-anion functional chalcohalides.