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Summer Research Fellowship Programme of India's Science Academies

Modulation of ground and excited state proton transfer reaction of E-2-((napthalen-2-ylimino)-methyl) phenol in micellar media

Nanigopal Bera

Indian Institute of Technology Kharagpur, West Bengal 721302

Prof. Nitin Chattopadhyay

Department of Chemistry, Jadavpur University, Jadavpur, Kolkata 700032

Abstract

The phenomena of ground and excited state proton transfer of the probe, E-2-((naphthalen-2-ylimino)-methyl) phenol (NMP), have been investigated in aqueous and various micellar media using steady state absorption and fluorometric techniques. Changes in the absorption and emission spectra of the probe in the aqueous as well as the micellar solutions upon addition of base, are ascribed to the proton transfer in both the ground and the excited states. Micelles affect the equilibrium of the proton transfer reaction by favoring or disfavoring the proton transfer process depending on the nature of the micelle. Existence of equilibrium between the normal and deprotonated species is established from the observation of the isosbestic points and the isoemissive points in the absorption and emission spectra respectively in all the environments. Acid dissociation constant in the ground state (pKa) and in the photoexcited state (pKa*) of NMP are determined from the steady state experiments using Weller’s method. Monitoring the ESPT reaction of the probe, critical micelle concentrations (CMC) of the three studied micelles, cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulphate (SDS) and Titron X-100 (TX-100) are also determined.

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