A MOLECULAR-ORBITAL STUDY OF EXCIPLEX STRUCTURE

The extended Huckel (EH) theory has been used to study the effect of altering the geometry and properties of the components of binary and ternary amine-anthracene exciplexes. Exciplex stability is found to be a function of orbital overlap between donor and acceptor components. Stable exciplex formation imparts charge transfer character to the complex as measured by the partial charge on the donor component. The formation of ternary exciplexes generally requires a donor-donor-acceptor arrangement, and such interaction leads to increased polarity and reduced donor-acceptor overlap. Weak binary exciplexes may prefer to undergo SN2-like substitution rather than form stable tenary complexes.