Structural Dynamics of Bismuth Triiodide in Solution Triggered by Photoinduced Ligand-to-Metal Charge Transfer

Abstract

Bismuth triiodide, BiI3, is one of the simplest bismuth halides, which have recently attracted considerable attention because of their promising properties. Here, we investigate the structural dynamics of a photoinduced reaction of BiI3 in solution phase using time-resolved X-ray liquidography (TRXL) and density functional theory (DFT) and time-dependent DFT (TDDFT) calculations. The photoreaction was initiated by excitation at 400 nm, which corresponds to the ligand-to-metal charge-transfer transition. The detailed structures and kinetic profiles of all relevant intermediate species from the TRXL data show that the trigonal planar structure of BiI3, which is predicted to be the most stable structure of the lowest excited state by TDDFT calculation, was not observed, and the photoreaction proceeds via two parallel pathways within the time resolution of 100 ps: (i) isomer formation to produce iso-BiI2–I, which relaxes back to the ground-state structure, and (ii) dissociation into BiI2· and I· radicals, which nongeminately recombine to generate ground-state BiI3 and I2.

Vibrational wavepacket dynamics in Fe carbene photosensitizer determined with femtosecond X-ray emission and scattering

“…A powerful method to disentangle the electronic and nuclear motions of 3d transition metal complexes during ultrafast nonadiabatic processes is time-resolved 1s-2p (Ka) and 1s-3p (Kβ) X-ray Emission Spectroscopy (XES) [10][11][12][13][14] combined with Wide Angle X-ray Scattering (WAXS) [15][16][17][18][19][20][21][22][23]. These experiments have been utilized to assign the electronic and structural motions during excited state dynamics [24][25][26] and to project the locations of conical intersections between excited state potential energy surfaces onto critical structural coordinates [27].…”

Reaction dynamics studiedviafemtosecond X-ray liquidography at X-ray free-electron lasers

“…A TRXL study at a synchrotron with 100 ps temporal resolution investigated the photochemical reaction dynamics of BiI 3 in acetonitrile solution and found that BiI 3 undergoes complex photoreactions involving two parallel reaction pathways. 34 Specifically, upon 400 nm excitation, a BiI 3 molecule (i) dissociates to yield radical fragments, and I˙, or (ii) isomerizes to form iso-BiI 2 –I. The photodynamics of BiI 3 is schematically depicted in Fig.…”

“…30 and 31)), and metal halides (HgI 2 , 32,33 HgBr 2 , 32,33 BiI 3 (ref. 34)), and photo-induced structural rearrangement of metal complexes ([Ir 2 (dimen) 4 ] 2+ (dimen = 1,8-diisocyano- p -menthane), 35 [Fe(btbip) 2 ] 2+ (btbip = 2,6-bis(3- tert -butyl-imidazol-1-ylidene)pyridine), 36 and [Pt 2 (P 2 O 5 H 2 ) 4 ] 4− 37 ). For macromolecular systems such as proteins, information about the overall structure such as size and shape can be obtained through the small-angle X-ray scattering (SAXS) region of TRXL signals, and more detailed structures such as the movement of alpha helices or beta sheets can be obtained through the signal from the wide-angle X-ray scattering (WAXS) region of TRXL signals.…”

Ultrafast Solution-Phase Photophysical and Photochemical Dynamics of Hexaiodobismuthate(III), the Heart of Bismuth Halide Perovskite Solar Cells

“…In this respect, halide coordination compounds of main group metal ions with an outer shell n s 2 configuration, such as Sn 2+ , Sb 3+ , Bi 3+ , and Te 4+ , have gained substantial attention. − In addition to the catalytic properties, these metal ions have found to be of use as dopants in many photophysical applications. − Recently, interest has been devoted to bismuth halide-based perovskites, a low-toxicity and low-cost alternative to lead-based halide perovskites, , due to their physical and optical properties in photovoltaic technologies. Many prospective bismuth-based perovskites adopt a MX 6 octahedral structural motif, − the photophysical properties of which have been of long-standing interest in Bi-doped crystals. , As of late, the photochemistry of Bi­( III )­I 6 3– ion and its parent Bi­( III )­I 3 compound has gained attention in room-temperature solutions as photoinitiated reactions that form I–I bonds.…”