Solvent effects on emission yield and lifetime for coumarin laser dyes. Requirements for a rotatory decay mechanism
Photophysical parameters have been determined for coumarin laser dyes in a variety of organic solvents, water, and mixed media. The response of fluorescence emission yield and lifetime to changes in solvent polarity was a sensitive function of coumarin substitution pattern. Most important were substituent influences which resulted in enlarged excited-state dipole moments for the fluorescent state. For dyes displaying sharp reductions in emission yield and lifetime with increased solvent polarity, protic media and particularly water were most effective in inhibiting fluorescence. The temperature dependence of emission yield and lifetime was measured for two solvent-sensitive dyes in acetonitrile and in a highly viscous solvent, glycerol. The quenching of coumarin fluorescence by oxygen for dyes with lifetimes > 2 ns was also observed. The dominant photophysical features for coumarin dyes are discussed in terms of emission from an intramolecular charge-transfer (ICT) excited state and an important nonradiative decay path involving rotation of the amine functionality (7-position) leading to a twisted intramolecular CT state (TICT). The role of excited-state bond orders involving the rotating group in determining the importance of interconversions of the type ICT ..-->.. TICT is discussed. 73 references, 1 figure, 3 tables.
- Research Organization:
- Boston Univ., MA
- OSTI ID:
- 5786342
- Journal Information:
- J. Phys. Chem.; (United States), Vol. 89:2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
ACETATES
SOLVENT PROPERTIES
ACETONITRILE
COUMARIN
ABSORPTION SPECTRA
EMISSION SPECTRA
CYCLOHEXANE
DIOXANE
ETHANOL
GLYCEROL
WATER
CHEMICAL REACTION KINETICS
DYE LASERS
EXPERIMENTAL DATA
FLUORESCENCE
RADIATIONLESS DECAY
RELAXATION
STRUCTURAL CHEMICAL ANALYSIS
ALCOHOLS
ALKANES
CARBOXYLIC ACID SALTS
CYCLOALKANES
DATA
DE-EXCITATION
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
ESTERS
HETEROCYCLIC COMPOUNDS
HYDROCARBONS
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
INFORMATION
KINETICS
LACTONES
LASERS
LIQUID LASERS
LUMINESCENCE
NITRILES
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
OXYGEN COMPOUNDS
PYRANS
REACTION KINETICS
SPECTRA
400301* - Organic Chemistry- Chemical & Physicochemical Properties- (-1987)
050503 - Nuclear Fuels- Uranium Enrichment- Laser Excitation- (-1989)