BiCuI4(Pyridine)5 a neutral ligand-supported compound of BiI3 and CuI

Abstract

Reaction of equimolar pyridine (Py) solutions BiI3 and CuI produces the Py-supported 1:1 bimetallic complex BiCuI4(Py)5 in quantitative yield. The title complex is only the second neutral complex to feature Cu−I−Bi bridging and shows an octahedral trans-[BiI4(Py)2] unit joined to a distorted tetrahedral CuI(Py)3 unit by an iodide bridge. The complex shows low thermal stability, decomposing under modest heating or vacuum to produce a mixture of BiI3 and CuI. Thus, it is a potential 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 [Cu(Py)3]+[BiI4(Py)2]−. Diffuse reflectance spectroscopy measurements show a strong absorption band with an optical bandgap energy of 1.94 eV. Theoretical density of states (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 π* acceptor orbitals.