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).

A novel A2B-type B(III)subchlorin has been synthesized for the first time in two ways possessing two different ester moieties upon macrocyclic periphery from meso-diethoxycarbonyl tripyrrane. Its photophysical and electrochemical properties have been explored. Introduction of the third meso-substituent resulted in the synthesis of the B(III)subchlorin as the major product with the formation of minor oxidized B(III)subporphyrin analogue. This subchlorin derivative was found to generate singlet oxygen much efficiently with quantum yield ([Formula: see text] 0.88.

Two novel classes of reduced triphyrins, namely triphachlorin and triphabacteriochlorin are realized via selective reduc-tion 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 de-trifluoromethylation of one CF3 moiety to form two isomeric triphabacteriochlorins 3 and 4, which exhibit blue shifted intense lowest energy absorption bands and intense emission (ϕf = 0.52, 0.36) while generating singlet oxygen very efficiently (ϕΔ: 0.88, 0.86). These reduced porphyrinoids show very high oxidative stability as they remain unchanged upon refluxing with DDQ in toluene.

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 CF 3 moiety to form two isomeric triphabacteriochlorins 3 and 4, which exhibit blue-shifted intense lowest-energy absorption bands and intense emission (ϕ f = 0.52 and 0.36, respectively) while generating singlet oxygen very efficiently (ϕ Δ = 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.

Meso-free B(III)subchlorin has been synthesized for the first time using meso-trifluoromethyl substituted tripyrrane, in trace quantity. It displays the most-blue shifted absorption and emission for subchlorins. This macrocycle was found to be completely resistant to oxidation and moderately generate singlet oxygen (34 %).