Charge-transfer excitation of molecular complexes in organic and organometallic chemistry

Electron donor-acceptor or EDA complexes are common precursors leading to a variety of organic and organometallic reactions, as indicated by the ubiquitous appearance of characteristic charge-transfer absorption bands. Structural effects of HOMO-LUMO interactions extant in donor-acceptor pairs, established by X-ray crystallography, are critical to the charge-tranfer excitation of various types of weak molecular complexes in which time-resolved picosecond spectroscopy identifies the nature of CT ion pairs. Their relevance to the transition state description of electrophile/nucleophile interactions is underscored in the detailed study of electrophilic aromatic nitration.