Porphycene-mediated photooxidation of benzylamines by visible light

Abstract

A variety of primary and secondary benzylic amines were oxidized efficiently to
N-benzylidenebenzylamines and imines, respectively, using 2,7,12,17-tetrapropylporphycene (H2TPrPc)
photocatalyst and blue light emitting diodes (LEDs). The photooxidation of 4-methoxybenzylamine in
the presence of H2TPrPc and its tin(IV) complex Sn(TPrPc)Cl2 was studied in detail in order to show
that operating mechanisms can be different depending on the photosensitizer type. Two experiments
involving solvent deuterium isotope effect and competitive quenching with DABCO provide evidence
for the singlet oxygen mechanism as the major pathway in the H2TPrPc-catalyzed reaction and the
predominance of the direct electron transfer from the photoexcited dye to the amine when the
Sn(TPrPc)Cl2 complex was used as a photocatalyst.