Structure and Nonlinear Optical Properties of the Cubic Cage Complex (n-Bu₄N)₃[Cu₃MoOS₃BrI₃]

Unlike the analogous (n-Bu₄N)₃[Cu₃MoOS₃Br₄], in which the cluster has a partially open cage structure, in the salt (n-Bu₄N)₃[Cu₃MoOS₃BrI₃] the anion forms a cubane-like cluster, consisting of a (Cu₃Mo) tetrahedron interlocked with an (S₃I) tetrahedron. The solid crystallizes in the cubic space group F4̄3c (a = 24.422(3) Å; Z = 8), the cluster adopting 12 allowed orientations randomly. This material exhibits a strong nonlinear optical absorption and a large, self-defocusing refractive index change. This behavior is intermediate between that of analogous nest-shaped clusters with an MoO group and cubic cage clusters with an MoS group, indicating that both the nature of the metal−chalcogenide and the overall skeletal structure of the cluster influence the nonlinear optical properties of the material.