Orientation effect of enhanced intersystem crossing in copper (II) porphyrin-free base porphyrin dimers

摘要

Intersystem crossing (ISC) enhanced by a remote unpaired electron through long-range interaction was studied in linear-type copper (II) porphyrin-free base porphyrin dimers in comparison with the gable -type dimers. The excited singlet state of the free base moiety is deactivated to its triplet manifolds quickly due to exchange interaction between the free base #pi#electrons and copper unpaired d elecytron. While the ISDC rates in the gable dimers show a simple relation with number of bonds of the linkage, two linear-type dimers behave differently. In the case of a p-phenyl bridged dimer, where the two porphyrin halves are almost parallel, the ISC rate is much larger than that expected from the simple through-bond coupling , which is applicable to the gable-type dimers. On the other hand , p-bip0henyl bridged dimer, in which two halves are not prallel, does not show such an effect. parallel orientation of the two terminals can play an important role in the long-range exchange coupling