IACS Department of Physical Chemistry, Indian Association for the Cultivation of Science, Kolkata, India Hydrogen Bonding Effects on Nonradiative Channels of Indole by Protic/Aprotic Polar Solvents Moitrayee Mukherjee and Tapas Chakraborty 64 th OSU International Symposium on Molecular Spectroscopy

IACS Introduction to indole fluorescence spectroscopy Stability of the hydrogen-bonded complexes CH 2 COOH CH NH 2 N H IndoleTryptophan  Indole is the chromophore of the amino acid tryptophan  Fluorescence spectra are sensitive to polarity of the medium N H

IACS Relative energies and dipole moments of the four lower energy states Sobolewski and Domcke, CPL 315 (1999) 293

IACS Electronic Spectroscopy of Indole---Formamide complex in a Supersonic Jet Short and Callis, JCP, 108 (1998) FE Spectrum DF Spectrum Tubergen and Levy, JPC, 95 (1991) 2175 N H C N H H O H Indole - Formamide

IACS Emission spectra of indole-formamide complex in a hydrocarbon solution Increasing temperature Pure solution of indole Indole + formamide Wavelength (nm) Absorption spectrum 287 nm

IACS Emission spectra of indole-formamide complex in a hydrocarbon solution Indole + formamide at RT Indole + formamide at 77K glass Wavelength (nm)

IACS FE spectra of Indole-alcohol complexes in a supersonic jet Hager and Wallace, J. Phys. Chem. 88 (1993) 5513 Lifetimes of the alcohols shorten upon formation of the complexes, explained as due to increased rate of ISC of the H-bonded complexes Ethanol Propanol Butanol N H C C H3H3 O H C H3H3 Indole - Propanol

IACS Emission spectra of the indole-isopropanol complex in hydrocarbon solutions Increasing temperature Wavelength (nm)

IACS Fluorescence Excitation Spectra of Indole-isopropanol complex Wavelength (nm) 77K glass Liquid at RT

IACS Acknowledgement Co-workers: 1.Prasenjit Pandey 2.Biman Bandyopadhyay 3.Anamika Mukhopadhyay Financial Support: Department of Science and Technology, Government of India