Synthesis of conformationally flexible porphyrin tweezers and their application in generation of singlet oxygen

The selected porphyrin acids such as 5-(4'-carboxyphenyl)-10,15,20-triphenylporphyrin, 5-(4'-carboxyphenyl)-10,15,20-tris-(4''-chlorophenyl)porphyrin, 5-(4'-carboxyphenyl)-10,15,20-tris-(4''-tertbutylphenyl)porphyrin and 5-(4'-carboxyphenyl)-10,15,20-(4''-pyridyl)porphyrin have been synthesised by reaction of two aldehydes with pyrrole in propionic acid.The coupling of 5-(4'-carboxyphenyl)-10,15,20-triarylporphyrins with pentan-1,5-diol in presence of EDC and DMAP give unsymmetrical bisporphyrins, which were metallated with zinc acetate to give different porphyrin tweezers. The singlet oxygen efficiency of porphyrin tweezers as photosensitizers have been quantified by monitoring the transformation of1,3-diphenylisobenzofuran (DPBF) to 1,2-dibenzoylbenzene by UV-visible spectroscopy. The quantum yield of formation of singlet oxygen for different porphyrin tweezers have been examined. The electron withdrawing group containing porphyrin tweezer is a better photosensitizer than electron donating group in generation of singlet oxygen. Copyright © 2017 VBRI Press.