Structural dynamics of bismuth triiodide in solution triggered by photoinduced ligand-to-metal charge transfer

초록

The interesting properties originating from the heavy metal center of a metal complex have offered prospects for useful applications, but at the same time understanding those features have been a challenging task due to the complicated nature of heavy-metal complexes. In particular, oxidation or reduction of the metal center opens a way to control the molecular structure as well as its properties and, as a result, the redox chemistry is a key factor that governs the chemical reactions of metal complexes. Redox reactions of metal complexes that can be initiated by light, so-called photoredox reaction, have been intensely investigated due to fundamental interest and wide applicability for various optoelectronic materials. Recently, bismuth(III) halide has been of great interest to researchers, especially in the field of photovoltaic solar cells and catalysis. For this reason, these compounds have been intensely studied mainly in solid state [1-2]. There are, however, relatively few studies on their photo-induced chemical dynamics in solution [3]. Here, we selected bismuth iodide complex (BiI3) as our model system to explore the photoinduced dynamics of bismuth halide, which can serve as a foundation for many applications of bismuth triiodide in condensed-phase chemistry. We investigated the structural dynamics of a photoinduced reaction of BiI3 in solution phase using time-resolved X-ray liquidography (TRXL) and density functional theory (DFT) calculations [4]. Briefly, the reaction was initiated by photoinduced ligand-to-metal charge transfer (LMCT) and the time-dependent X-ray scattering patterns were measured and analyzed. In particular, we captured the transiently formed iso-isomer as well as photofragments of BiI3 and unraveled their detailed structures and kinetics. Our experimental findings were well supported by quantum chemical calculations. Furthermore, our recent results of femtosecond-TRXL experiment on the same molecular system using XFEL will also be