Three-center systems for energy pooling: Quantum electrodynamical theory

Fundamental theory is developed for three-body resonance energy transfer in the condensed phase, involving two donors and a single acceptor. This ener gy pooling mechanism is responsible for recent experimental observations on trichromophore molecules and other moieties, manifest for example in the p hotochemistry of organo dyes and rare-earth ion doped crystals. A full quan tum. electrodynamical (QED) treatment of this pooling is developed and form ulated with the aid of a novel diagrammatic method, which proves to have se veral advantages over Feynman diagram methods. Following derivation of the rate of energy pooling for an isolated group of chromophores, the electroni c influences of the medium across which the energy migrates are embedded in the theory and duly discussed. Energetic constraints on the acceptor molec ule are elucidated and shown to account for a variety of postulated mechani sms: the geometry of the three-center system is itself shown to exercise co nsiderable control over the dominant mechanism. By extension, the theory is amenable to the study of more complex energy transfer arrangements, such a s those observed in dendrimer chemistry and the light-harvesting photochemi stry of the photosynthetic unit.