Charge transfer induced excited state twisting of N,N-dimethylaminobenzylidene-1,3-indandione in solution

Nonradiative excited-state relaxation via charge transfer induced twisting of N,N-dimethylaminobenzylidene-1,3-indandione (DMABI) in solution was investigated by means of picosecond transient absorption and femtosecond fluorescence spectroscopy. The analysis of the experimental data allows us to distinguish between different reaction stages of the molecular twisting in excited and ground states, as well as to consider the molecular dynamics along reactive (twisting) and nonreactive (solvation) coordinates. Quantum chemical calculations of the electronic structure of DMABI and its dependence on the molecular conformation are discussed in order to identify the bond(s) involved in the twisting reaction. It is found that such a twisting bond is the C=C double bond, which is substantially weakened in the excited state.