Catalysis of a photochemical quantum chain process -: Optimal conditions for catalyzed quantum chain cis-trans photoisomerizations of a styrylpyrene

In an experimental study of catalyzed photosensitized cis-trans isomerization of 1-(3,5-di-tertbutylstyryl)pyrene, three different catalysts, anthracene, 9-methylanthracene and 9,10-di-chloroanthracene were used. The most efficient catalytic process was observed when anthracene was used as the catalyst. The quantum yield was 11.5 times higher than that of the uncatalyst isomerization. The use of different catalyst shows that the quantum yield for the photoisomerization strongly depends on properties of the added catalyst. The most important properties of the catalyst seem to be proper triplet energy and long triplet lifetime. The limits for the catalysis of cis-trans isomerization chain process was also investigated by model calculation. From this calculation it is concluded that a high quantum yield is not equivalent with efficient catalysis. The most efficient catalysis is reached when the triplet state energy of the catalyst is around 1.5 kcal/mol above the triplet energy of the E-isomer. For this optimum of the catalytic effect, quantum yield in the absence of the catalyst is close to unity. (C) 2001 Elsevier Science B.V. All rights reserved.