Generation of singlet oxygen by indotricarbocyanine dyes in low-polarity media |
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Authors: | M P Samtsov E S Voropai K N Kaplevskii D G Mel’nikov |
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Institution: | (1) A. N. Sevchenko Institute of Applied Physical Problems, 7 ul. Kurchatova, Minsk, 220064, Belarus |
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Abstract: | We present the results of a study of the spectral luminescence properties of three groups of indotricarbocyanine dyes, each
of which is formed from compounds with the same cation and different anions. In high-polarity solvents, in the absorption
and emission spectra of the dyes we see one type of center; in low-polarity solvents, due to the presence of different ionic
forms of the dyes (free ions, contact ion pairs), we observe either one type or two types of centers. By analysis of the luminescence
of molecular oxygen in the 1.27 μm spectral region, we determined the efficiency of photosensitization of 1O2 formation by dyes in deuterated solvents. We have shown that in low-polarity solvents, the yield for singlet oxygen generation
is higher for indotricarbocyanine dyes which are found in the contact ion pair state and which also contain a heavy atom (I)
in the anion. We have observed that an increase in the fraction of contact ion pairs in solution as the dye concentration
increases or when an additional salt is introduced leads to an increase in the quantum yield for generation of singlet oxygen.
In polar deuterated acetonitrile, the counterion has no effect on the efficiency of photosensitization of oxygen by the dyes.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 5, pp. 684–693, September–October, 2008. |
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Keywords: | indotricarbocyanine dyes ion pairs spectral properties singlet oxygen |
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