Inter- and intramolecular excited state proton transfer in 2-hydroxy-9H-carzole-1-carboxylic acid.
Absorption, fluorescence and fluorescence excitation spectroscopy and single photon counting time dependence spectrofluorimetry have been used to study the inter- and intramolecular excited state proton transfer (ESIPT) reactions in 2-hydroxy-9H-carbazole-1-carboxylic acid (2-HCA). Except in cyclohexane and water (pH 5) dual fluorescence is observed in rest of the solvents used. Normal Stokes shifted band seems to originate from 2-HCA-1-c and tautomer emission band from the tautomer formed by ESIPT in 2-HCA-1-c followed by structural reorganization. Both these emission band systems originate from the same ground state species. AM1 and CNDO/S-CI calculations have been carried out to establish the identity of the species. Different prototropic equilibria have been determined and discussed.
Nayak
M K
MK
Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India.
Dogra
S K
SK
D002227:Carbazoles / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D011522:Protons; D012995:Solubility; D012997:Solvents / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
D002227:Carbazoles; D002264:Carboxylic Acids; D011522:Protons; D012997:Solvents; C041514:carbazole