UV-laser photochemistry of the azoalkane 1-phenyl-2,3-diazabicyclo(2. 2. 2)oct-2-ene: detection and lifetime determination of the triplet diradical 1-phenyl-1,4-cyclohexadiyl by time-resolved UV spectroscopy (flash photolysis) and by trapping with molecular oxygen
The short lifetime (tau/sub T/) of the triplet diradical 1,4-cyclohexadiyl compared to the relatively long-lived 1,3-cyclopentadiyl was previously rationalized in terms of Salem's orbital orientation rule. It was argued that in its boat conformation the 1,4-cyclohexadiyl suffers fast intersystem crossing through favorable orientation of the orbital lobes for spin-orbit coupling, resulting in a short lifetime and thus inefficient trapping by /sup 3/O/sub 2/. The authors provide experimental evidence that phenyl stabilization promotes conformational relaxation to the favored twist-boat triplet ground state, resulting in the long-lived 1-phenyl-1,4-cyclohexadiyl. The generation of the 1,4-diradical via photolysis and product formation (with and without oxygen trapping) is summarized, together with rate constants.
- Research Organization:
- Univ. of Wuerzburg, Germany, F.R.
- OSTI ID:
- 5674261
- Journal Information:
- J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 109:24; ISSN JACSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400500* -- Photochemistry
ALKANES
AZO COMPOUNDS
CHEMICAL REACTIONS
CONFIGURATION INTERACTION
CONFORMATIONAL CHANGES
DECOMPOSITION
ELECTROMAGNETIC RADIATION
ELEMENTS
HYDROCARBONS
LASERS
LIFETIME
NONMETALS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXYGEN
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
RADIATIONS
REACTION INTERMEDIATES
ULTRAVIOLET RADIATION