Direct irradiation of mono-, di-,
and trisubstituted triphenylamine
derivatives in acetonitrile as solvent with light of 254 nm has been
systematically investigated, revealing that the exo/endo carbazole derivatives were formed as the main
photoproducts from modest to good yields for triphenylamines substituted
with electron-donor and neutral substituents. The kinetic profiles
of the photoreaction were also recorded, and the consumption rate
constants (k) were measured. These kinetic parameters
show dependence on the nature of the substituents, and linear Hammett
correlations were carried out to showcase the substituent effect.
On the other hand, the spectroscopic behavior of the electron-rich
substituted triphenylamines has been analyzed, suggesting that the
fluorescence emission spectra display a mirror image of the lower
energy absorption bands, while for those amines bearing electron-acceptor
groups the formation of charge-transfer complexes and their fluorescence
emissions constitute the main deactivation pathway of the photoreaction.