Excited enantiomeric quenching

Trigonal ML3 metal complexes exist as optically active pairs. The complexes can show enantiomeric selective binding to DNA and in excited state quenching.<34) One of the optically active enantiomers of RuLj complexes binds more strongly to chiral DNA than does the other enantiomer. In luminescence quenching of racemic mixtures of rare earth complexes, resolved ML3 complexes stereoselectively quench one of the rare earth species over the other. 35-39 Such chiral recognition promises to be a useful fundamental and practical tool in spectroscopy and biochemistry. 

The area of stereoselective electron transfer has attracted considerable attention in recent years. The nature of the products obtained depends upon the enantiomer which is undergoing reaction. For example, excited state quenching of A-[Ru(bpy)3] by racemic [Co(acac)j] leads to an enantiomeric excess of A-[Co(acac)j]. 

Miranda et al. studied the excited-state behavior of chiral drugs bound to BSA and HSA. Inclusion of carprofen 101 (Scheme 1.22) in HSA significantly lengthened the triplet-state lifetime of 101 as a result of more rigid surroundings and the suppression of self-quenching of 101. The complexation of enantiomeric 101 with HSA caused a significant difference in triplet lifetime, and the lifetime of (5)-101-HSA complex is 4 times shorter than that of (/ )-101-HSA complex. Irradiation of 101 alone in aqueous buffer solution led to a polymerization of 101. However, dechlorinated carprofen 102 was... 

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