To Be or Not To Be Symmetric: That Is the Question for Potentially Active Vibronic Modes

Abstract

Electronic spectra often exhibit vibronic structure when vibrational and electronic transitions occur in concert. Theory reveals (1) that orbital symmetry considerations determine specific roles played by the nuclear degrees of freedom and (2) that the vibrational excitation is often highly regiospecific, that is, attributable to an identifiable subset of atoms within the molecule. Spectra obtained from a chromium(III) complex involving a macrocyclic ligand and two axially disposed butadiynide groups nicely illustrate many of the concepts involved.

Excited-state charge polarization and electronic structure of mixed-cation halide perovskites: the role of mixed inorganic–organic cations in CsFAPbI3

“…Similar effects have been observed before in chromium(III) complexes. 30 The average octahedra tilting angle was 15.54 while the octahedra next to the Cs cations show strong distortions coming from broken symmetry of surrounding atoms. For instance, tilting angles, vertical Pb-I bond length, and vertical I-Pb-I bond angles as much as 29 , 3.36 Å, and 168 were obtained for highly distorted octahedra next to caesium cations.…”