Crystal Structure of the Second-Order Nonlinear Optical Addition Complex AsI3·3S8

Abstract

The arsenic triiodide–sulfur adduct, AsI3·3S8 is a new nonlinear optical acceptor–donor intermolecular complex of relatively high second-order susceptibility, χ(2) ca. 10–11 m V–1. Single crystals formed by addition of AsI3, and octasulfur, S8, in the molar ratio 1 : 3 were grown from solution. The space group is R3m, a 24.739(2) Å, c 4.412(3)�Å, V 2338(1) Å3, Z 3. The arsenic triiodide molecules occupy C3v symmetry sites with the molecular three-fold symmetry axis parallel to the polar crystal c axis. S8 retains the crown conformation. Each of the three iodine atoms of the acceptor molecule, AsI3, is involved in charge-transfer contacts to the chalcogen donor atoms of the partner S8 molecules. The adduct structure has been analysed in the context of remarkable differences between nonlinear optical properties of AsI3·3S8 and the isomorphous complexes, CHI3·3S8 and SbI3·3S8.