Solvation and rotational relaxation of coumarin 153 and 4-aminophthalimide in a new hydrophobic ionic liquid: Role of N-H...F interaction on solvation dynamics

The solvent relaxation and rotational dynamics of coumarin 153 and 4-aminophthalimide have been investigated in a hydrophobic room-temperature ionic liquid, 1-(2-methoxyethyl)-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate. The dynamic fluorescence Stokes shift measurements suggest that the average solvation time is highly dependent on the probe molecules. The average solvation time of 4-aminophthalimide is estimated to be six times larger than that of coumarin 153. Rotational coupling constant value of 4-aminophthalimide is also found to be larger than that of coumarin 153. Hydrogen bonding interaction between the probe molecule (4-aminophthalimide) and the ionic liquid is found to play a role on the dynamics of solvation in the present medium. (C) 2011 Elsevier B.V. All rights reserved.