GROUND-STATE AND EXCITED-STATE ASSOCIATION - CHIRAL RECOGNITION BETWEEN 2,2'-DIHYDROXY-1,1'-BINAPHTHYL AND AMINES

Stability constants of complexes in the ground state of S(-)-2,2'-dihydroxy-1,1'-binaphthyl(binaphthol, BiOH) with S(-)- and R(+)-1-phenylethylamine (PEA), S(+)- and R(-)-1-cyclohexylethylamine (CHEA), S(-)- and R(+)-N,N-dimethylphenylethylamine (DMPEA), S(-)- and R(+)-(1-naphthylethylamine) (NEA), (1S,2R)-(+)- and (1R,2S)(-)-2-dimethylamine-1-phenylpropanol (N-methylephedrine, NME) were determined in a series of solvents. Differences were found in complexation in the system S(-)-BiOH-R(-)-CHEA-chiral alcohols in acetonitrile. The S(-)- and R(+)-BiOH fluorescence quenching in the presence of chiral amines mentioned above was studied in some solvents. Distinct differences were only found in acetonitrile. Weak fluorescence of the excited ion pair with hydrogen bond was observed for all investigated systems in all solvents used. A mechanism is proposed involving charge-transfer complexes as well as exciplexes. The influence of chiral solvents indicates the participation of trimolecular intermediates in the ground state. In the excited state proton transfer leading to an ion pair may explain the chiral discrimination in acetonitrile.