Photochemical synthesis and photophysical properties of coumarins bearing extended polyaromatic rings studied by emission and transient absorption measurements

Minoru Yamaji, Yuma Hakoda, Hideki Okamoto, Fumito Tani

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

We prepared a variety of coumarin derivatives having expanded π-electron systems along the direction crossing the C3-C4 bond of the coumarin skeleton via a photochemical cyclization process and investigated their photophysical features as a function of the number (n) of the added benzene rings based on emission and transient absorption measurements. Upon increasing n, the fluorescence quantum yields of the π-extended coumarins increased. Expanding the π-electron system on the C3-C4 bond of the coumarin skeleton was found to be efficient for increasing the fluorescence ability more than that on the C7-C8 bond. Introducing the methoxy group at the 7-position was also efficient for enhancing the fluorescence quantum yield and rate of the expanded coumarins. The non-radiative process from the fluorescence state was not substantially influenced by the expanded π-electron system. The competitive process with the fluorescence was found to be intersystem crossing to the triplet state based on the observations of the triplet-triplet absorption. The effects of the expanded π-electron systems on the fluorescence ability were investigated with the aid of TD-DFT calculations.

Original languageEnglish
Pages (from-to)555-563
Number of pages9
JournalPhotochemical and Photobiological Sciences
Volume16
Issue number4
DOIs
Publication statusPublished - 2017

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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