Excited-State Proton Transfer in Chiral Environments: Photoracemization of BINOLs.

We have studied excited-state proton transfer (ESPT) from chiral proton donors to chiral and achiral acceptors. The key role of the exergonicity of the reaction and the transition-state position along the reaction coordinate for the existence of an enantiomeric effect was established. This effect was observed for "super" photoacids (ΔG ≪ 0) and vanished for endergonic reactions (ΔG > 0) where a "late" transition state similar to planar achiral binaphtholate anion occurs.

Importance of hydrogen-bonding sites in the chiral recognition mechanism between racemic D3 terbium(III) complexes and amino acids.

The perturbation of the racemic equilibrium of luminescent D3 terbium(III) complexes with chelidamic acid (CDA), a hydroxylated derivative of 2,6-pyridine-dicarboxylic acid (DPA), by added chiral biomolecules such as L-amino acids has been studied using circularly polarized luminescence and 13C NMR spectroscopy. It is shown in this work that the chiral-induced equilibrium shift of [Tb(CDA)3](6-) by L-amino acids (i.e.