10.1021/ja0113652.s001 Frederick D. Lewis Frederick D. Lewis Xiaobing Zuo Xiaobing Zuo Rajdeep S. Kalgutkar Rajdeep S. Kalgutkar Jill M. Wagner-Brennan Jill M. Wagner-Brennan Miguel A. Miranda Miguel A. Miranda Enrique Font-Sanchis Enrique Font-Sanchis Julia Perez-Prieto Julia Perez-Prieto Temperature-Dependent Photochemistry of 1,3-Diphenylpropenes. The Di-π-Methane Reaction Revisited American Chemical Society 2001 unactivated processes activation parameters singlet state rate constants quantum yields rearrangement Kinetic modeling isomerization product ratios nonradiative decay unactivated fluorescence temperature range process yields intersystem 2001-11-09 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Temperature-Dependent_Photochemistry_of_1_3-Diphenylpropenes_The_Di-_-Methane_Reaction_Revisited/3635253 The temperature-dependent photochemical behavior of 1,3-diphenylpropene and several of its 3-substituted derivatives has been investigated over a wide temperature range. The singlet state is found to decay via two unactivated processes, fluorescence and intersystem crossing, and two activated processes, trans,cis isomerization and phenyl-vinyl bridging. The latter activated process yields a diradical intermediate which partitions between ground-state reactant and formation of the di-π-methane rearrangement product. Kinetic modeling of temperature-dependent singlet decay times and quantum yields of fluorescence, isomerization, di-π-methane rearrangement, and nonradiative decay provides rate constants and activation parameters for each of the primary and secondary processes. Substituents at the 3-position are found to have little effect on the electronic spectra or unactivated fluorescence and intersystem crossing pathways. However, they do effect the activated primary and secondary processes. Thus, the product ratios are highly temperature dependent.