Light-induced Energy Transfer in Model Systems

It is not often that the triplet state properties of cofacial dimers are reported but, in an interesting variation on the normal theme, this has been done for a series of naphthalenophanes. Here, the triplet state is accessed via sensitization with benzophenone and it is shown that the excited state behaviour depends markedly on the conformation of the superstructure. Both monomer and excimer states are apparent in the transient absorption records, according to the extent of 

Electronic energy transfer from an excited state donor to a suitable acceptor is a fundamental process in photochemistry and is of prime importance in artificial photosynthesis. A variety of mechanisms exist by which energy migration and transfer can take placeand such processes have been used to create the so-called antenna effect . In particular, much research has concentrated on designing molecular systems in which an organic host is used to bind a lanthanide cation in such a way that photoexcitation of the host results in intramolecular energy transfer to the bound cation.  

In order to mimic electronic energy transfer from the light-harvesting complex to the special pair of the reaction centre complex, a variety of bichromophoric molecules have been synthesized in which terminal donor and acceptor units are separated by a transparent spacer group. Provided the geometry of the dyad is known, especially the separation distance and mutual orientation, it becomes possible to consider the rates of intramolecular energy transfer in terms of 

---