State-selective photochemistry of singlet oxygen precursors: kinetics and wavelength dependence of the photodissociation of anthracene endoperoxides
The Journal of Physical Chemistry
Oo level of the uncomplexed tetrazine following 6a' excitation of the complex. The calculations also predict very little 0' complex emission following 16a' excitation of the complex. In all cases these predictions and the experimentally observed results are in complete agreement. Conclusions Science Foundation. This simple, one-parameter RRKM model is in semiquantitative agreement with all the static and time-resolved data for which comparison is possible. The detailed validity of this model
... ty of this model can be unambigously tested only by direct time-resolved spectroscopic studies of both complexed and uncomplexed molecules in specific vibrational states. Acknowledgment. This work was supported by the National Registry No. Ar, 7440-37-1; s-tetrazine, 290-96-0. The photochemical behavior of the two isomeric endoperoxides (9,10-PMO2 and 1 ,4-PMO2) of 1,4-dimethyl-9,lO-diphenylanthracene was found to differ in their kinetics and reaction efficiencies. Consistent with the work of Rigaudy et al. and Brauer et al. on a related endoperoxide we find that the generation of IO2 is wavelength dependent, occurring from upper excited singlet states of the endoperoxide, whereas bond cleavage of the 0-0 endoperoxide bond occurs principally from the lowest excited singlet and triplet states. Results of picosecond kinetics and absolute quantum yield measurements are discussed in terms of various concerted and nonconcerted mechanisms for the formation of IO2 and the anthracene fragment.