The new quaternary lanthanum copper oxysulfide La 3 CuO 2 S 3 has been synthesized by the reaction of La 2 S 3 and CuO at 1223 K. This compound crystallizes in space group Pnma of the orthorhombic system with four formula units in a cell of dimensions at 153 K of a ¼ 14:0318ð7Þ Å , b ¼ 3:9342ð2Þ Å , and c ¼ 12:5212ð6Þ Å . The structure of La 3 CuO 2 S 3 consists of a three-dimensional framework of interconnected LaO n S 8Àn bicapped trigonal prisms and CuS 4 tetrahedra. Optical absorption measurements on a La 3 CuO 2 S 3 single crystal led to derived band gaps of 2.01 eV in both the [010] and [001] directions. r 2003 Elsevier Science (USA). All rights reserved.