Molecular dynamics simulations of the solvation of coumarin 153 in a mixture of an alkane and an alcohol

Molecular dynamics simulations are applied to the preferential solvation of coumarin 153 (C153) by alcohol in an alcohol/alkane mixture, indicated by recent steady-state and time-resolved spectroscopic measurements.(1) Simulations of weakly polar mixtures are done for the ground and the excited states of C153, using detailed models of the dye. Solvation of C153 by the alcohol is almost negligible in the ground state, with correspondingly little effect on the absorption spectrum of the dye, whereas preferential solvation of the excited state leads to a large solvation shift of the fluorescence spectrum, in agreement with experiment. The simulated solvation shell and its dynamics are described and related to the solvation shifts.