Assessment of solvent effect on the relaxation dynamics of milrinone

We report a study of the effect of solvent properties (polarity, H-bonding and viscosity) on the relaxation dynamics of milrinone (MIR) by using steady-state UV–vis absorption, emission and picosecond emission techniques. The major solvent effect on the steady-state absorption and emission spectra is due to specific interactions between solvent molecules and different sites of MIR, although the effect of medium polarity is not negligible. Time-resolved experiments provided more information. The observed effect on the relaxation dynamics is due to H-bonding acceptor ability, polarity and viscosity of the solvent. The result is explained in terms of the presence of an intramolecular charge-transfer reaction and twisting motion. The anisotropy decay data suggest that MIR rotates under stick boundary conditions. We believe that these results might be of importance for improving drugs design and may help to understand the interactions of MIR and other drugs with the environment.