Two noncentrosymmetric quaternary tin chalcoarsenates, CS2SnAs2S9 (1) and Cs2SnAs2Se9 (2), were synthesized by the polychalcoarsenate flux method. Compound 1 crystallizes in the orthorhombic space group Pmc2(1) with a = 7.386(3) Angstrom, b = 14.614(5) Angstrom, c = 14.417(5) Angstrom, and Z = 4. Compound 2 crystallizes in the monoclinic space group P2(1) with a = 7.715(5) Angstrom, b = 17.56(1) Angstrom, c = 7.663(5) Angstrom, beta = 115.86(1)degrees, and Z = 2. Both structures contain the same tin-centered molecular cluster anions {Sn[AsQ(2)(Q(2))][AsQ(Q(2))(2)]}(2-) (Q = S,Se) separated by Cs cations. The Sn4+ ion is in a distorted octahedral environment coordinated by two different pyramidal-shaped tridentate ligands, [AsQ(2)(Q(2))](3-) and [AsQ(Q(2))(2)](3-). These compounds absorb visible light at energies above 1.98 and 1.45 eV for 1 and 2, respectively. Differential thermal analysis revealed that 1 melts at 350 degreesC and on cooling gives a glass. The glass recrystallizes at 268 degreesC upon subsequent heating. Compound 2 melts at 258 degreesC.