PNNL

Abstract

Reaction of equimolar pyridine (Py) solutions BiI3 and CuI produces the Py-supported 1:1 bimetallic complex BiCuI4Py5 in quantitative yield. The title complex is only the second neutral complex to feature Cu-I-Bi bridging and shows an octahedral trans-(BiI4Py2) unit joined to a distorted tetrahedral CuIPy3 unit by an iodide bridge. While air-stable, the complex shows low thermal stability, decomposing under modest heating or vacuum to produce a mixture of BiI3 and CuI. Thus, it is a potentially convenient entry/precursor to BiI3/CuI chemistry. Natural Localized Molecular Orbital (NLMO) calculations were performed to analyze the nature of the Cu-I-Bi bonds revealing that the title compound lies on the cusp of being such a salt, (CuPy3)+(BiI4Py2)-. Diffuse reflectance spectroscopy measurements shows a strong absorption band with an optical bandgap energy of 1.94 eV. Theoretical density of state (DOS) and time-dependent density functional theory (TD-DFT) experiments to map the electronic structure assign the primary electronic transition as a mixed halide/metal-to-ligand charge transfer between Cu-I-Bi donor orbitals and Py ?* acceptor orbitals.