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Solvent effects on the photophysics of 3-(benzoxazol-2-yl)-7-(N,N-diethylamino)chromen-2-one

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Abstract

The photophysics of 3-(benzoxazol-2-yl)-7-(N,N-diethylamino)chromen-2-one was studied in different solvents and in SDS micelles. This compound presents characteristics which include an S0 → S11(π,π*) transition with a 1(n,π*) perturbative component, due to the electronic coupling between the diethylamino group and the coumarin ring, considerable solvatochromism, dual fluorescence and high fluorescence quantum yields in almost all solvents studied. The electronic structure of the S1 and S2 excited states permits vibronic coupling between them, making configurational changes of the S2 excited state possible, leading to the formation of an S2(TICT) state. Analysis of the TCSPC data indicates an equilibrium between the S2(TICT) and S1(LE) states in favour of the former. In protic solvents, the hydrogen bonding between the solvent and the diethylamino moiety results in the formation of an S2(HICT) state, making internal conversion an important deactivation process. Quantum mechanical calculations for the isolated molecule show that the diethylamino group in the S2(TICT) state is twisted at least 56° from the plane of the coumarin ring, with partial electronic decoupling between—NEt2 and the coumarin ring. This twisting angle must be positively influenced by solute-solvent interactions. ΦST is found to be small, but not negligible. However, ΦΔ can be considered negligible, an indication that T1 is a short-lived state. Based on the experimental data and theoretical calculations, the most probable sequence for the first excited states, including the TICT state, is T1(n,π*) < S2(TICT) < S1(π,π*) ≈ S2(n,π*).

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Authors and Affiliations

  1. Instituto de Química/Laboratório de Fotoquímica, Universidade Federal de Uberlândia, P.O. Box 593, CEP 38400-089, Uberlândia, MG, Brazil

    Antonio Eduardo da Hora Machado, Divinomar Severino, Juliana Ribeiro, Rodrigo De Paula & Jacques Antonio de Miranda

  2. IQSC/Laboratório de Fotoquímica, Universidade de São Paulo, CEP 13560-970, São Carlos, SP, Brazil

    Marcelo Henrique Gehlen & Hueder Paulo Moisés de Oliveira

  3. Departamento de Psicologia e Educação, Universidade de São Paulo, FFCLRP, CEP 14040-901, Ribeirão Preto, SP, Brazil

    Mauricio dos Santos Matos

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  1. Antonio Eduardo da Hora Machado
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  2. Divinomar Severino
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  3. Juliana Ribeiro
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Correspondence to Antonio Eduardo da Hora Machado.

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Machado, A.E., Severino, D., Ribeiro, J. et al. Solvent effects on the photophysics of 3-(benzoxazol-2-yl)-7-(N,N-diethylamino)chromen-2-one. Photochem Photobiol Sci 3, 79–84 (2004). https://doi.org/10.1039/b308121d

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