Solvation dynamics of coumarin 153 in dimethylsulfoxide–water mixtures: Molecular dynamics simulations

Abstract

We present results of molecular dynamics simulations of solvation dynamics of coumarin 153 in dimethylsulfoxide ͑DMSO͒-water mixtures of different compositions (x D ϭ0.00, 0.25, 0.32, 0.50, 0.75, and 1.00͒ using an all-atom model for the solute probe. Results are reported for the global solvation responses of the simulated systems, as well as for the separate contributions from each cosolvent and the individual solute-site couplings to water and DMSO. The solvation dynamics is predominantly given by DMSO's contribution, even at low ͑25%͒ DMSO content, because of the preferential solvation of the probe. We find that the water molecules are only mildly coupled to the charge transfer in the coumarin, resulting in a small, largely diffusive, water relaxation component. Simulation results, including solvation responses, characteristic times, and Stokes shifts are compared with recent fluorescence upconversion experimental measurements showing good agreement for the relaxation but significant differences for the shifts.

Polarizability anisotropy relaxation in pure and aqueous dimethylsulfoxide

“…18 The translational and reorientational dynamics of these mixtures investigated through MD simulations are in good agreement with experimental NMR data, 9 showing minima for the self-diffusion coefficients and slowest reorientational dynamics for mixtures with composition near 33% DMSO. Simulation studies of the dielectric relaxation 31 and solvation dynamics 34 over the whole composition range yield results consistent with available measurements 12,23 and unveils important microscopic details about the behavior of the mixtures. MD simulation have also provided valuable insights into the underlying mechanisms associated to the dynamics of hydrogen bonding in these mixtures 33 through the reactive-flux approach.…”

“…21 Similar discrepancies have been found in MD simulations of the solvation dynamics of a coumarin probe in these mixtures. 34 As pointed out by Castner and co-workers, 21 the singlemolecule polarizability anisotropy of DMSO is much larger than that of water, since the electronic density of this molecule is dominated by the oxygen atom alone. The electronic structure calculations yield a ratio of ␥ D 2 /␥ W 2 ϭ116.1.…”

Coumarin 153 emission thermochromism studied in non-specifically and specifically interacting solvents

“…4). Skaf and coworkers [44] performed an MD simulation of C153 dissolved in a water-DMSO mixture and in these pure solvents separately. They did not observe any indication of the presence of a hydrogen bond between C153 and DMSO.…”

Solvatochromism and Solvation Dynamics in CO2-Expanded Liquids

“…The DCS/CH 3 CN+C0 2 system is an excellent prototype for studying preferential solvation dynamics due to the similar size, shape, and inertial properties of the solvent components, and also for its lack of specific solute-solvent interactions. There have been several simulation studies of preferential solvation in conventional liquid mixtures (22)(23)(24)(25)(26)(27)(28), however, few have examined nonspecific preferential solvation dynamics. Day and Patey simulated dynamics of preferential ion solvation in binary Stockmayer mixtures (26).…”