Photophysics and photochemistry of arylmethyl radicals in liquids
A series of arylmethyl radicals (including Ph/sub 2/CH (diphenylmethyl), 10,11-dihydro-5H-dibenzo(a,d)cyclohepten-5-yl (=DBHP.), Ph/sub 2/CCH/sub 3/, Ph/sub 2/C-c-Pr, and Ph/sub 3/C.) have been produced pulse radiolytically in a variety of solvents and then excited with lambda = 347 nm ruby laser pulses. Ph/sub 2/CCH/sub 3/, Ph/sub 2/C-c-Pr, and Ph/sub 3/C undergo a solvent independent monophotonic photochemical reaction with high quantum yield. This reaction is proposed to occur from the first excited doublet state and to yield a fluorenyl-type radical. Ph/sub 2/CH and DBHP strongly fluoresce upon relaxation to their ground doublet state. Fluorescence spectra as well as excited doublet-doublet absorption spectra of these radicals have been recorded and their lifetimes and fluorescence quantum yields determined. No photochemistry is observed from the lowest excited state of both of these radicals. The difference in photoreactivity of the two groups of radicals (Ph/sub 2/CH and DBHP vs. Ph/sub 2/CCH/sub 3/, PH/sub 2/C-c-Pr, and Ph/sub 3/C) is rationalized as resulting from the degree of twist of the phenyl groups out of the central molecular plane. A solvent-dependent consecutive biphotonic photochemistry from excited states higher than the lowest excited doublet state is, however, observed for the Ph/sub 2/CH and DBHP radicals. A mechanism to rationalize this photochemistry is proposed. 26 references, 12 figures, 1 table.
- Research Organization:
- Argonne National Lab., IL
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 5863261
- Journal Information:
- J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 107:1; ISSN JACSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400500* -- Photochemistry
ABSORPTION SPECTROSCOPY
ACETONITRILE
ALCOHOLS
ALKANES
ALKENES
AROMATICS
ARYL RADICALS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COMPARATIVE EVALUATIONS
CORRELATIONS
CYCLOALKENES
DATA
DATA ANALYSIS
ELECTROMAGNETIC RADIATION
EMISSION SPECTROSCOPY
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
ETHANOL
EXCITATION
EXCITED STATES
EXPERIMENTAL DATA
FLUORESCENCE SPECTROSCOPY
HYDROCARBONS
HYDROXY COMPOUNDS
INFORMATION
IRRADIATION
KINETICS
LASER RADIATION
LEAST SQUARE FIT
MATHEMATICAL MODELS
MAXIMUM-LIKELIHOOD FIT
MONITORING
NITRILES
NUMERICAL DATA
NUMERICAL SOLUTION
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PULSED IRRADIATION
RADIATIONS
RADICALS
REACTION KINETICS
SOLVENT PROPERTIES
SPECTROSCOPY