Multipathway photodimerization of 2-methylthianaphthene 1,1-dioxide. An example of heavy-atom effect on intersystem crossing in a 1,4 diradical

Journal Article · Tue Apr 10 23:00:00 EST 1979 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00502a037· OSTI ID:6259668

Hopkinson, M J; Schloman, Jr, W W; Plummer, B F; Wenkert, E; Raju, M

The photodimerization of 2-methylthianaphthene 1,1-dioxide (MeTND) at 313 nm produces two photodimers whose structures are shown to be anti head to head (HH) and anti heat to tail (HT) about the cyclobutane ring. The major isomer produced is always the HH dimer in oxygen-free solutions. Fluorescence quenching of MeTND by 1,4-diazabicyclo(2.2.2)-octane produces a linear Stern--Volmer relation that yields an estimated singlet lifetime for MeTND of 2 x 10/sup -9/S. The kinetics of the photodimerization of MeTND were studied as a function of concentration of MeTND, solvent, triplet quenchers, and triplet sensitizers. The data suggest that the HH and HT dimers arise from different excited-state precursors. A monomeric excited triplet is the proposed progenitor of the HH dimer while an excimer is proposed to be the precursor of the HT dimer. Heavy-atom perturbation is found to occur on the S/sub 1/ ..-->.. T/sub 1/ transition of MeTND but is not effective for the radiationless T/sub 1/ ..-->.. S/sub 0/ transition. The triplet-sensitized dimerization of MeTND is found to be sensitive to heavy-atom perturbation and this is interpreted as a spin-orbital perturbation in intersystem crossing in the 1,4 diradical. 6 figures, 6 tables.

• Research Organization: Trinity Univ., San Antonio, TX
• OSTI ID: 6259668
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 101:8; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
400500 -- Photochemistry
AROMATICS
BENZENE
BROMINATED ALIPHATIC HYDROCARBONS
BROMINATED AROMATIC HYDROCARBONS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DATA
DATA FORMS
DIMERIZATION
DISTURBANCES
EXPERIMENTAL DATA
FLUORESCENCE
HALOGENATED ALIPHATIC HYDROCARBONS
HALOGENATED AROMATIC HYDROCARBONS
HEAT TREATMENTS
HYDROCARBONS
INFORMATION
ISOLATED VALUES
ISOMERS
KINETICS
LUMINESCENCE
NUMERICAL DATA
ORGANIC BROMINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
POLYMERIZATION
PRECURSOR
QUANTITY RATIO
QUENCHING
REACTION KINETICS
REAGENTS
SENSITIZERS