The reaction of (NH4)(2)[MoO2S2], CuI, and Et(4)NI in solid state produces a twin-nest-shaped cluster compound [Et(4)N](4)[Mo2O2S6Cu6I6] The cluster anion consists of two nest-shaped fragments interconnected through a four-membered Cu(I)(2)Cu ring. The structure of the cluster has been characterized by X-ray diffraction : monoclinic, space group C2/c, a = 24.680(1) Angstrom, b = 21.328(5) Angstrom, c = 13.638(4) Angstrom, beta = 114.51(3)degrees, V = 6532(4) Angstrom(3), Z = 4, R = 0.043, R(w) = 0.054. The cluster easily decomposes into two halves when treated with ligands such as py or PPh(3). The cluster also exhibits both strong nonlinear optical absorption and optical self-defocusing effect (effective alpha(2) = 4 x 10(-10) m W-1, n(2) = -6 x 10(-17) m(2) W-1 when measured with a 2 x 10(-3) M acetonitrile solution).