H. G. O. Becker, T. Lehmann, J. Zieba
1989
Citations
0
Influential Citations
4
Citations
Journal
Journal Fur Praktische Chemie-chemiker-zeitung
Abstract
Zinc meso-tetraphenylporphyrin (ZnTPP) forms triplet exciplexes with different arenediazonium salts (p-Et2N, p-MeO, p-Me, p-t-Bu, p-H, p-Cl, p-Br) and p-benzoquinone, and a singlet exciplex with oxygen (probably formed after energy transfer from excited ZnTPP to 3O2 to yield 1O2). The absorption spectra of these exciplexes are nearly identical and – except of pronounced fine structures – similar to the spectrum of 3(ZnTPP)*. By means of WARE treatment of flash-photolytically determined rate constants or of quantum yields equilibrium constants, lifetimes and further data of diazonium salt exciplexes are determined. The equilibrium constants and lifetimes are very similar and amount to about 104 M−1 and 20 μs, respectively. The equilibrium constants of the oxygen and p-benzoquinone exciplexes are determined by competition experiments; they amount also to about 104 M−1. The diazonium salt exciplexes belong to the charge-shift type. Their equilibrium constants are, therefore, independent of the solvent polarity, as is interestingly also observed for the oxygen exciplex which formally belongs to the charge-separation type. The p-benzoquinone exciplex dissociates in acetonitrile as has been found also by other authors.