Fluorescence and phosphorescence of acetone in neat liquid and aqueous solution studied by QM/MM and PCM approaches

Abstract

Electronic singlet and triplet nπ * absorption and emission energies of acetone in vacuum, neat liquid and aqueous solution have been calculated. Electronic states of acetone in solution have been modelled using combined molecular dynamics-quantum mechanics/molecular mechanics techniques and the polarizable continuum model. In addition, we have compared density functional theory based results to corresponding coupled cluster singles and doubles predictions. Theoretical results have also been compared to experimental data. In general, we have obtained a good description of solvent effects on the absorption energies. However, modelling of excited states explicitly is still a challenge for the applied approaches, as the solvent shifts of the singlet nπ * emission have been considerably underestimated and also the solvent shift related to the Stokes shifts of fluorescence was predicted to have incorrect sign compared to available experimental data.

Solvent effect on electronic absorption, fluorescence, and phosphorescence of acetone in water: Revisited by quantum mechanics/molecular mechanics (QM/MM) simulations

“…However, Adias et al's recent QM/MM calculations based on classical molecular dynamics (MD) trajectories predicted a solvent shift around 0.14 eV for fluorescence of acetone in water, 30 in contrast with the understanding concluded from the works by Rörig et al, Öhrn and Karlström, that the solvent effect for fluorescence of acetone in water should be negligible or small. In the recent years, the triplet state and the phosphorescence of acetone in aqueous solution have also been explored by classical 30 and QM/MM 31 simulation techniques. These works estimated T 1 → S 0 emission energy of acetone in water to be 2.35-2.67 eV 30,31 and the solvent shift for it was determined to be around 0.14 eV.…”

“…Later, Canuto's group 29 re-examined their previous classical Monte Carlo simulation work, 26 and they found including the solute's electronic polarizations of both the ground and the excited states through an iterative procedure will decrease the solvent effect of n ← π * fluorescence from 0.23 eV to 0.01-0.08 eV. However, Adias et al's recent QM/MM calculations based on classical molecular dynamics (MD) trajectories predicted a solvent shift around 0.14 eV for fluorescence of acetone in water, 30 in contrast with the understanding concluded from the works by Rörig et al, Öhrn and Karlström, that the solvent effect for fluorescence of acetone in water should be negligible or small. In the recent years, the triplet state and the phosphorescence of acetone in aqueous solution have also been explored by classical 30 and QM/MM 31 simulation techniques.…”

“…[1][2][3][4][5][6][7][8][9][10] Although many computational works [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] have been devoted to the study of electronic absorption in aqueous acetone, its fluorescence spectra received limited theoretical attentions [26][27][28][29][30] due to the difficulty of simulating excited state dynamics. Moreover, the magnitude of the solvent effect on the n ← π * (S 1 → S 0 ) emission is still controversial to some extent despite of the fact that it has been well recognized that the water effect on the n → π * (S 0 → S 1 ) absorption is a blueshit of ∼0.2-0.3 eV.…”

“…In the recent years, the triplet state and the phosphorescence of acetone in aqueous solution have also been explored by classical 30 and QM/MM 31 simulation techniques. These works estimated T 1 → S 0 emission energy of acetone in water to be 2.35-2.67 eV 30,31 and the solvent shift for it was determined to be around 0.14 eV. 30 However, these results are still difficult to rationalize due to the absence of experimental data for the phosphorescence process of aqueous acetone.…”

Computational Spectroscopy by Classical Time‐Dependent Approaches

“…p à ) triplet state of acetone. Despite the large number of experimental [116,122] and theoretical [118,[123][124][125] works on acetone, certainly one of the most studied organic compounds, its triplet state has been less investigated and mainly in the gas phase [126][127][128]. However, due to its relatively long lifetime in solution (about 20-50 ms), [129] triplet acetone has a quite rich and interesting chemistry and photochemistry.…”