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Photophysics and Rotational Dynamics of a Hydrophilic Molecule in a Room Temperature Ionic Liquid
Author(s) -
Chatterjee Aninda,
Maity Banibrata,
Ahmed Sayeed Ashique,
Seth Debabrata
Publication year - 2015
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/php.12472
Subject(s) - rotational diffusion , viscosity , chemistry , relaxation (psychology) , ionic liquid , solvent , activation energy , diffusion , chemical physics , ionic bonding , molecule , thermodynamics , organic chemistry , ion , psychology , social psychology , physics , catalysis
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 ([N 1888 ][ NT f 2 ]). 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 [N 1888 ][ NT f 2 ] 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.