Decay dynamics of the triplet state of 2,6-dimethyl-4H-1-benzothiopyran-4-thione in solution

Di †use reÑectance, emission and transient di †use reÑectance measurements of the spectra and decay kinetics of several aromatic thioketones supported on cellulose have provided information concerning the second excited singlet state, the lowest triplet state, and transient chemical intermediates formed when these materials S 2 , T 1 , are excited in the near UV. Thermally activated delayed Ñuorescence from the lowest excited singlet state, is S 1 , a minor component of the emission at room temperature, but not at 77 K because back-intersystem crossing is eliminated, resulting in a substantial lengthening of the triplet lifetime. At room temperature, the triplet states have lifetimes of the order of microseconds and the chemical intermediates have lifetimes of hundreds of microseconds. Comparisons of the triplet spectra in polar and non-polar media with those on cellulose show that is of p,p* conÐguration on the solid support, as expected if the thione is adsorbed in a polar T 1 microenvironment. The triplet decay times, but not the spectra, indicate that the thiones are in di †erent microenvironments when they are adsorbed from acetonitrile compared with methanol. The latter have decay times characteristic of single molecules ; the former may indicate the thiones are adsorbed as aggregates. Singlet molecular oxygen, observed directly by transient emission at 1270 nm, is formed with near unit O 2 (1* g ), efficiency from the thione triplets in Ñuid acetonitrile solution, but oxygen has no measurable e †ect on the triplet spectra and decay times when the thione is supported on cellulose.

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Triplet states of aromatic thioketones supported on cellulose

Sikorski¹,

Wilkinson²,

Bourdelande³

et al. 1999

Phys. Chem. Chem. Phys.

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Triplet state decay of some thioketones in solution

Sikorski¹,

Khmelinskii²,

Augustyniak³

et al. 1996

Faraday Trans.

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Decay dynamics of the triplet state of 2,6-dimethyl-4H-1-benzothiopyran-4-thione in solution

Cited by 2 publications

References 27 publications

Triplet states of aromatic thioketones supported on cellulose

Triplet states of aromatic thioketones supported on cellulose

Triplet state decay of some thioketones in solution

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