Fluorescence Quenching and Photoreactions of 2,3-Diazabicyclooct-2-enes. A Case of Charge Transfer and Hydrogen Atom Transfer

Article abstract of DOI:10.1021/jo00231a032

A variety of organic compounds have been found to quench the long-lived fluorescence of 2,3-diazabicyclo<2.2.2>oct-2-ene (DBO), but photochemical reactions take place only with good hydrogen atom donors and tetrahalomethanes.A hydrogen isotope effect on k_q of 1.7-3.0 was observed with 1,3- and 1,4-cyclohexadiene.While both quenchers photoreduced DBO, the 1,3-isomer also dimerized to a mixture characteristic of triplet diene.The results are rationalized in terms of the usual encounter complex and ion pair except that the former can undergo hydrogen transfer or react with 1,3-cyclohexadiene.A second case of photochemically induced electron transfer fragmentation was found in the reaction of 1-phenyl-DBO with bromotrichloromethane.