RESUMO
Two novel classes of reduced triphyrin(2.1.1), namely, triphachlorin and triphabacteriochlorin, are realized via selective reduction of the newly synthesized 7,12-bis(trifluoromethyl)triphyrin(2.1.1) 1 using p-tosylhydrazide. Triphachlorin 2 displayed red-shifted absorption (580 nm). Harsher conditions, however, led to a unique direct detrifluoromethylation of one CF3 moiety to form two isomeric triphabacteriochlorins 3 and 4, which exhibit blue-shifted intense lowest-energy absorption bands and intense emission (Ïf = 0.52 and 0.36, respectively) while generating singlet oxygen very efficiently (ÏΔ = 0.88 and 0.86, respectively). These reduced porphyrinoids show very high oxidative stability as they remain unchanged upon refluxing with 2,3-dichloro-5,6-dicyanobenzoquinone in toluene.
RESUMO
The first direct fabrication of A2B- and A3-type B(III)subchlorins from meso-ethoxycarbonyl-substituted tripyrrane has been realized by condensation with appropriate acid chlorides (benzoyl chloride, butyryl chloride, and ethyl chlorooxoacetate). The aliphatic acid chloride-based annulation reaction is new to subporphyrinoid chemistry. The phenyl (6a)- or n-propyl (6b)-substituted derivatives could be oxidized to the corresponding B(III)subporphyrins upon refluxing with DDQ, whereas the triethoxycarbonyl moiety (6c) was found to be resistant to oxidation and exhibits the most red-shifted absorption (587 nm) and emission (604 nm). The study indicates that absorption and emission behaviors of the B(III)subchlorin can be tuned by the introduction of electron-rich or electron-deficient substituents at the meso-position. B(III)subchlorins 6a and 6c generate singlet oxygen efficiently (44 and 40%, respectively) and, thus, may find application as potential photosensitizers in photodynamic therapy (PDT).