Comparative photophysics of sapphyrin derivatives: Effects of confused and fused pyrrole rings

Jong Min Lim, Iti Gupta, Hiroyuki Furuta, Dongho Kim

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    5 Citations (Scopus)

    Abstract

    We have investigated the photophysical properties of [22] π-conjugated pentapyrrolic systems, sapphyrin, N-confused and N-fused sapphyrins, with a particular focus on the effects of confused and fused pyrrole rings on their electronic structures using steady-state and time-resolved spectroscopic methods, two-photon absorption cross-section (σ(2)) measurements and quantum mechanical calculations. The absorption spectra of N-confused and N-fused sapphyrins exhibit relatively red-shifted features compared to sapphyrin. In parallel with these spectral features, the reduced HOMOLUMO gaps were observed in going from sapphyrin to N-fused sapphyrin. In the analysis of the anisotropy of the induced current density (AICD), N-confused and N-fused sapphyrins show that extra π-electrons in confused and fused pyrrole rings contribute to the extension of their π-conjugation pathways. Slightly larger twophoton absorption cross-section values of N-confused and N-fused sapphyrins (3250 and 3900 GM) than that of sapphyrin (2900 GM) also reflect an enhanced π-conjugation effect due to bicyclic and endocyclic extensions in π-conjugation pathways, respectively. The excited singlet and triplet state lifetimes of N-confused sapphyrin were determined to be 60 ps and 1 μs, respectively, due to conformational change and acceleration of nonradiative decay processes, being in a sharp contrast with those of sapphyrin (2.4 ns and 13 μs, respectively). In the case of N-fused sapphyrin, very short singlet excited-state lifetime of 5 ps was detected probably due to the excited-state NH-tautomerization process which enhances nonradiative decay processes.

    Original languageEnglish
    Pages (from-to)858-864
    Number of pages7
    JournalJournal of Porphyrins and Phthalocyanines
    Volume15
    Issue number9-10
    DOIs
    Publication statusPublished - 2011

    All Science Journal Classification (ASJC) codes

    • Chemistry(all)

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