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Photophysics and Spectroscopic Properties of 3-Benzoxazol-2-yl-chromen-2-one by Antonio Eduardo da Hora Machado; Jacques Antonio de Miranda; Silvana Guilardi; David Ernest Nicodem; Divinomar Severino is a Chemistry article available to read on EtoBox.

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The photophysics of 3-benzoxazol-2-yl-chromen-2-one was studied in different solvents. High molar absorptivities, between 14,800 and 22,900 dm3/mol cm, were observed for the absorption peak related to the S0 --> S1 transition which suggests a pi --> pi\* character. This compound presents a limited solvatochromism, attributed to the benzoxazole group, and high fluorescence quantum yields, phi(f). The fluorescence quantum yield is lowered with the increase of solvent polarity, favouring the participation of internal conversion as deactivation path of the S1 state. The Stokes shift shows that the excited state is stabilised with increasing solvent polarity. The dipole moment was estimated by ab initio calculations as being between 5.28 and 5.62 Debye for S1, and 4.75 Debye for S0. Phosphorescence was not observed. A small but not negligible quantum yield of singlet oxygen generation (phidelta = 0.15) was measured in chloroform. The geometric parameters obtained by semi-empirical calculation (PM3) are in good agreement with crystallographic data, showing a r.m.s. deviation of 0.153 A for the superposition of both structures. The predicted structure is all planar, while the crystallogra

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Author

Antonio Eduardo da Hora Machado; Jacques Antonio de Miranda; Silvana Guilardi; David Ernest Nicodem; Divinomar Severino

Publisher

Elsevier Science; Elsevier ; Elsevier Ltd.; Pergamon Press Ltd.; Elsevier BV (ISSN 1386-1425)

Published

2003

Language

EN

Field

Chemistry (Physical Sciences)