Intramolecular charge transfer in pyrromethene laser dyes: photophysical behaviour of PM650. |
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Authors: | F López Arbeloa J Ba?uelos Prieto V Martínez Martínez T Arbeloa López I López Arbeloa |
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Institution: | Departamento de Química Física, Universidad del Pais Vasco-EHU, Apartado 644, 48080 Bilbao, Spain. qfploarf@lg.ehu.es |
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Abstract: | Absorption and fluorescence (steady-state and time-correlated) techniques are used to study the photophysical characteristics of the pyrromethene 650 (PM650) dye. The presence of the cyano group at the 8 position considerably shifts the absorption and fluorescence bands to lower energies with respect to other related pyrromethene dyes; this is attributed to the strong electron-acceptor character of the cyano group, as is theoretically confirmed by quantum mechanical methods. The fluorescence properties of PM650 are intensively solvent-dependent. The fluorescence band is shifted to lower energies in polar/protic solutions, and the evolution of the corresponding wavelength with the solvent is analysed by a multicomponent linear regression. The fluorescence quantum yield and the lifetime strongly decrease in polar/protic solvents, which can be ascribed to an extra nonradiative deactivation, via an intramolecular charge-transfer state (ICT state), favoured in polar media. |
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Keywords: | charge transfer photophysics pyrromethene dyes quantum mechanics calculations solvent effects |
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