Synthesis and photophysical properties of β-triazole bridged porphyrin–coumarin dyads†
Abstract
Novel copper(II) β-triazole bridged porphyrin–coumarin conjugates have been synthesized in good to excellent yields via a copper(I)-catalyzed Huisgen 1,3-dipolar cycloaddition reaction of copper(II) 2-azido-5,10,15,20-tetraphenylporphyrin with various alkyne-substituted coumarins. These newly prepared copper complexes of β-triazole-bridged porphyrin–coumarin dyads were successfully demetallated in the presence of conc. H2SO4 at 0 °C to afford the corresponding free-base porphyrins which on zinc insertion by using Zn(OAc)2·2H2O in a chloroform–methanol mixture at 25 °C produced zinc(II) β-triazole bridged porphyrin–coumarin dyads in good yields. The synthesized products were characterized spectroscopically and evaluated for their photophysical properties by using UV-Vis and fluorescence spectroscopy. The preliminary results revealed a significant intramolecular energy transfer from the coumarin subunit to the porphyrin moiety in the case of some β-triazole bridged porphyrin–coumarin dyads.