title: Anomalous excited-state dynamics of lucifer yellow CH in solvents of high polarity: evidence for an intramolecular proton transfer.
abstract: The photophysics of the fluorescent probe Lucifer yellow CH has been investigated using fluorescence spectroscopic and computational techniques. The nonradiative rate is found to pass through a minimum in solvents of intermediate empirical polarity. This apparently anomalous behavior is rationalized by considering the possibility of predominance of different kinds of nonradiative processes, viz. intersystem crossing (ISC) and excited-state proton transfer (ESPT), in solvents of low and high empirical polarity, respectively. The feasibility of the proton transfer is examined by the structure determined by the density functional theory (DFT) calculations. The predicted energy levels based on the time-dependent density functional theory (TD-DFT) method in the gas phase identifies the energy gap between the S(1) and nearest triplet state to be close enough to facilitate ISC. Photophysical investigation in solvent mixtures and in deuterated solvents clearly indicates the predominance of the solvent-mediated intramolecular proton transfer in the excited state of the fluorophore in protic solvents.
authors.affiliation: Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, India.
authors.forename: Debashis
authors.initials: D
authors.lastname: Panda
authors.forename: Padmaja P
authors.initials: PP
authors.lastname: Mishra
authors.forename: Saumyakanti
authors.initials: S
authors.lastname: Khatua
authors.forename: Apurba L
authors.initials: AL
authors.lastname: Koner
authors.forename: Raghavan B
authors.initials: RB
authors.lastname: Sunoj
authors.forename: Anindya
authors.initials: A
authors.lastname: Datta
mesh_terms: D003198:Computer Simulation; D007546:Isoquinolines / Q000737:chemistry*; D008956:Models, Chemical; D011522:Protons; D012680:Sensitivity and Specificity; D012997:Solvents / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods
chemical_list: D007546:Isoquinolines; D011522:Protons; D012997:Solvents; C017475:lucifer yellow