Experimental and computational studies of novel Sudan-I dye modified conjugated oligomers: Efficient 1O2 generation and antileishmanial characteristics

Abstract Introduction of multi-functionality in conducting polymers via modification with dyes is a facile technique that can be adopted to design various kinds of photosensitive and fluorescent polymers. Keeping this in mind, the present work reports for the first time modification of conventional conducting polymers such as polyaniline (PANI) and poly(ophenylenediamine) (POPD) with Sudan-I dye by microwave-assisted method. The chemical structure of prepared oligomers was confirmed by experimental as well as theoretical FT-IR and 1H NMR studies, while the electronic transitions were explored via UV visible analysis. The morphology of the oligomers was confirmed by TEM analysis. The quantum yield (Ф) values were calculated to be 0.40 and 0.54 for SY-PANI and SY-POPD respectively, by fluorescence studies. The oligomers were evaluated for their singlet oxygen (1O2) generation tendency, cytotoxicity and antileishmanial activity. The oligomers were found to effectively generate 1O2 upon excitation under different laser sources. The 1O2 quantum yield and quantum efficiency were found to be 0.13 and 0. 29% under red laser irradiation, while under green laser source, the same values were calculated to be 0.59% and 0.63%. The cytotoxicity analysis revealed that the oligomers were less cytotoxic on human macrophage cell line and significantly inhibited the growth and proliferation of Leishmania parasite – a characteristic which could be exploited for the development of new, effective and least toxic technique to treat leishmaniasis.