title: Photophysics and Rotational Dynamics of a Hydrophilic Molecule in a Room Temperature Ionic Liquid.
abstract: We have studied the photophysics and rotational diffusion of hydrophilic solute 7-(N, N'-diethylamino)coumarin-3-carboxylic acid (7-DCCA) in a room temperature ionic liquid methyltrioctylammonium bis(trifluoromethylsulfonyl) imide ([N1888 ][NTf2 ]). Comparison of activation energies of viscous flow and nonradiative decay shows that the photophysical properties of 7-DCCA are not guided by the bulk viscosity of the medium but are dependent on the specific solute solvent interaction and structural heterogeneity of the medium. The rotational relaxation behaviour of 7-DCCA in [N1888 ][NTf2] shows significant deviation from the Stokes Einstein Debye hydrodynamic model of rotational diffusion. This is indicative of the influence of specific solute solvent interaction on the rotational relaxation behaviour of 7-DCCA. Comparison of activation energy of rotational relaxation with activation energy of viscous flow clearly reinforces our assumption that the structural heterogeneity of the medium and specific solute solvent interaction plays a dominant role on the rotational diffusion instead of bulk viscosity.
authors.affiliation: Department of Chemistry, Indian Institute of Technology Patna, Patna, Bihar, India.
authors.forename: Aninda
authors.initials: A
authors.lastname: Chatterjee
authors.affiliation: Department of Chemistry, Indian Institute of Technology Patna, Patna, Bihar, India.
authors.forename: Banibrata
authors.initials: B
authors.lastname: Maity
authors.affiliation: Department of Chemistry, Indian Institute of Technology Patna, Patna, Bihar, India.
authors.forename: Sayeed Ashique
authors.initials: SA
authors.lastname: Ahmed
authors.affiliation: Department of Chemistry, Indian Institute of Technology Patna, Patna, Bihar, India.
authors.forename: Debabrata
authors.initials: D
authors.lastname: Seth