meso-Phenyl-triazole bridged porphyrin-coumarin dyads: Synthesis, characterization and photophysical properties

• Diverse coumarinoalkynes have been synthesized in good yields.
• A modified and high yielding procedure for 5-(4-azidophenyl)-10,15,20-triphenylporphyrin has been developed.
• An efficient methodology for the synthesis of novel meso-phenyl-triazole bridged porphyrin-coumarin dyads is described.
• Photophysical studies revealed an efficient intramolecular energy-transfer between porphyrin and coumarin scaffolds.

Novel zinc (II) meso-phenyl-triazole bridged porphyrin-coumarin dyads have been synthesized in good to excellent yields through copper (I)-catalyzed Huisgen 1,3-dipolar cycloaddition reaction of zinc (II) 5-(4-azidophenyl)-10,15,20-triphenylporphyrin with diverse coumarinoalkynes in dimethylformamide containing ascorbic acid at 80 °C. These compounds successfully underwent demetallation in the presence of concentrated hydrochloric acid to afford the corresponding free-base porphyrins which on treatment with nickel acetate in chloroform-acetic acid mixture produced various nickel (II) meso-triazole bridged porphyrin-coumarin dyads in good yields. All the newly synthesized products were characterized on the basis of spectral data and elemental analyses. The preliminary photophysical results revealed a significant intramolecular energy transfer between porphyrin core and coumarin moiety in the case of zinc porphyrin analogues.

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