Quenching of fluorescence for fluoro derivatives of the laser dye DCM in polar solutions |
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Authors: | A A Turban S L Bondarev V N Knyukshto A P Stupak |
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Institution: | (1) Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70 prosp. Nezavisimosti, Minsk, 220072, Belarus |
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Abstract: | We used fluorescence spectroscopy and nanosecond flash photolysis to study the photophysical properties of the laser dye 4-dicyanomethylene-2-methyl-6-(p-dimethylamino)styryl-4H-pyran
(DCM) and its two fluoro derivatives: (E)-2-〈2-2-(4-dimethylaminophenyl)ethenyl]-6-trifluoromethyl-4H-4-pyranylidene〉malononitrile
(DCMF3) and (E)-2-〈2-2-(4-dimethylaminophenyl)ethenyl]-6-n-heptafluoro-propyl-4H-4-pyranylidene〉 malononitrile (DCMF7), in
nonpolar n-hexane, mixtures of low-polarity toluene and polar dimethylsulfoxide (DMSO), n-propanol at room temperature and
at 77 K. The fluorescence quantum yield Φfl of the laser dye DCM increases linearly as the polarity of the binary solvent mixture (toluene+DMSO) increases, from 0.08
in toluene to 0.80 in DMSO. The dependence of Φfl on the polarity of the mixture toluene+DMSO for DCMF3 and DCMF7 reaches a maximum for a small amount (∼2 vol.%) of added
polar DMSO; and with further increase in the DMSO concentration (≥50 vol.%), the fluorescence of the fluoro derivatives of
DCM is practically completely quenched. The quantum yield for intersystem crossing ΦST for DCM, DCMF3, and DCMF7 is no greater than 0.01 in solutions of different polarities. We discuss the mechanisms for nonradiative
deactivation of the electronic excitation energy for the fluoro derivatives compared with DCM.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 5, pp. 606–612, September–October, 2006. |
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Keywords: | laser dye charge transfer fluorescence quantum yield solvent polarity |
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