Showing papers by "Prasun Mukherjee published in 2006"
TL;DR: In this paper, an analysis of the sub-nanosecond dynamic solvation of ionic liquids in particular and ionic solutions in general is provided, based on the theory that solvation relaxation in ionic fluids, in the nonglassy and nonsupercooled regimes, can be understood rather simply in terms of the dielectric spectra of the solvent.
Abstract: An analysis is provided of the subnanosecond dynamic solvation of ionic liquids in particular and ionic solutions in general. It is our hypothesis that solvation relaxation in ionic fluids, in the nonglassy and nonsupercooled regimes, can be understood rather simply in terms of the dielectric spectra of the solvent. This idea is suggested by the comparison of imidazolium ionic liquids with their pure organic counterpart, butylimidazole (J. Phys. Chem. B 2004, 108, 10245-10255). It is borne out by a calculation of the solvation correlation time from frequency dependent dielectric data for the ionic liquid, ethylammonium nitrate, and for the electrolyte solution of methanol and sodium perchlorate. Very good agreement is obtained between these theoretically calculated solvation relaxation functions and those obtained from fluorescence upconversion spectroscopy. Our comparisons suggest that translational motion of ions may not be the predominant factor in short-time solvation of ionic fluids and that many tools and ideas about solvation dynamics in polar solvents can be adapted to ionic fluids.
72 citations
TL;DR: Owing to the importance of determining the amount of initial solvation that is missed in a given experiment with finite time resolution, a method of estimating the intramolecular contribution to the reorganization energy is discussed and is compared with an alternative method.
Abstract: Steady-state and time-resolved Stokes shift data for the probe coumarin 153 in two imidazoles, six imidazolium-based ionic liquids, and several other solvents are presented. These results are consistent with our original suggestion (J. Phys. Chem. B 2004, 108, 10245−10255) that initial solvation is dominated by the organic moiety of the ionic liquid, and they show that for the imidazole-based liquids initial solvation is in all cases very rapid. Solvation by methylimidazole and butylimidazole is complete in 100 ps, and all of the imidazolium ionic liquids demonstrate similarly rapid initial solvation. Owing to the importance of determining the amount of initial solvation that is missed in a given experiment with finite time resolution, we discuss a method of estimating the intramolecular contribution to the reorganization energy. This method yields 2068 cm-1 and is compared with an alternative method.
69 citations
TL;DR: Exploiting the use of ionic liquids capable of accommodating specific structures thus provides a deeper insight into how solutes interact with these fascinating and interesting solvents that are gaining ever increasing interest in the scientific community.
Abstract: Dynamic solvation of the dye, coumarin 153, is compared in an ionic liquid that forms micelles in water against the bulk solvent This provides the unprecedented opportunity of investigating the behavior of the ionic liquid in two globally different configurations It is proposed that the imidazolium moiety is in both cases responsible for the majority of the solvation, which manifests itself in the first 100 ps Exploiting the use of ionic liquids capable of accommodating specific structures thus provides a deeper insight into how solutes interact with these fascinating and interesting solvents (at least those that are imidazolium based) that are gaining ever increasing interest in the scientific community
54 citations
TL;DR: The photoreceptor pigment of the heterotrich ciliate, Maristentor dinoferus, has been characterized and it is remarkable that while the pigments are structurally similar in S. coeruleus and M. dinorfus, in the former there is an abrupt photophobic response, whereas in the latter there is a slow response toward light.
Abstract: The photoreceptor pigment of the heterotrich ciliate, Maristentor dinoferus, has been characterized. It is structurally similar to those of Stentor coeruleus and Blepharisma japonicum but differs significantly in that it bears no aromatic hydrogens. The structure of the pigment, maristentorin, is based upon the hypericin skeleton, and its spectra are nearly identical to those of hypericin but shifted toward the red. Within experimental error, its fluorescence lifetime is identical to that of hypericin, ∼5.5 ns in dimethylsulfoxide. It is remarkable that while the pigments are structurally similar in S. coeruleus and M. dinoferus, in the former there is an abrupt photophobic response, whereas in the latter there is a slow response toward light. The roles of the hypericin-like pigments in the heterotrich ciliates are discussed as potentially analogous in Maristentor.
36 citations
TL;DR: Coumarin 153 exhibits negligible nonspecific binding to the surface of apomyoglobin, and its interactions with both the apo and holo proteins are studied to confirm the appropriateness of the system of coumarin153 and apomyobic for the investigation of solvation by the protein matrix.
Abstract: In order to provide a thorough characterization of a system with which to study the dielectric response of a protein, a well-defined system complex of a fluorescent probe and protein is required. We have argued that such a system is provided by coumarin 153 and apomyoglobin (Photochem. Photobiol. 79, 440–446 [2004]). In order to demonstrate further that coumarin 153 exhibits negligible nonspecific binding to the surface of apomyoglobin, we study its interactions with both the apo and holo proteins. We further make a similar comparison with 8-anilino-1-naphthalenesulfonic acid, for which an NMR structure with apomyoglobin has been obtained. Our results confirm the appropriateness of the system of coumarin 153 and apomyoglobin for the investigation of solvation by the protein matrix.
10 citations