Jump to main content
Jump to site search

Issue 20, 2017
Previous Article Next Article

Investigation of the push–pull effects on β-functionalized benzoporphyrins bearing an ethynylphenyl bridge

Author affiliations

Abstract

A series of β-pyrrole functionalized push–pull porphyrins with amine push groups linked via an ethynylphenyl spacer, and cyclic imide or carboxylic esters as pull groups have been newly synthesized and characterized. The β-pyrrole functionalized ethynylphenyl spacer extends the conjugation of the porphyrin π-system, as reflected by their red-shifted absorbance and fluorescence spectra. The computed structures revealed no steric hindrance between the porphyrin π-system and the β-substituents. The calculated HOMO and LUMO of compounds WJ2 and WJ3 display significant segregation, where the electron density in the HOMO and LUMO is mainly located at the donor component and the acceptor component, respectively. The orbital segregation is likely attributed to the introduction of the electron-donating amine group at the porphyrin periphery. Electrochemical studies revealed the expected lower HOMO–LUMO gap as a result of the facile oxidation and reduction of the push–pull porphyrins. As a consequence of the push–pull effects, a reduction in fluorescence intensity and lifetime was observed, especially for compound WJ3 having two electron-donating amino groups and a strongly electron-withdrawing cyclic imide group. Femtosecond transient absorption spectral studies revealed the successful formation of the singlet excited state in all of these push–pull porphyrins. Due to the occurrence of intramolecular charge transfer-type interactions, relaxation of the singlet excited state was found to be faster in compound WJ3 compared to other two derivatives in polar solvent but not in nonpolar solvent. Such charge transfer-type interactions from the triplet excited state were also observed in the case of compound WJ3 in benzonitrile. The present findings bring out the importance of push–pull effects in governing the ground and excited (singlet and triplet) state properties of free-base porphyrins.

Graphical abstract: Investigation of the push–pull effects on β-functionalized benzoporphyrins bearing an ethynylphenyl bridge

Back to tab navigation
Please wait while Download options loads

Supplementary files

Publication details

The article was received on 02 Jan 2017, accepted on 24 Apr 2017 and first published on 24 Apr 2017


Article type: Paper
DOI: 10.1039/C7CP00024C
Citation: Phys. Chem. Chem. Phys., 2017,19, 13182-13188
  •   Request permissions

    Investigation of the push–pull effects on β-functionalized benzoporphyrins bearing an ethynylphenyl bridge

    R. G. Waruna Jinadasa, M. B. Thomas, Y. Hu, F. D'Souza and H. Wang, Phys. Chem. Chem. Phys., 2017, 19, 13182
    DOI: 10.1039/C7CP00024C

Search articles by author