Study of the fluorescent properties of partially hydrogenated 1,1'-bi-2-naphthol-amine molecules and their use for enantioselective fluorescent recognition

The fluorescent properties of a series of H(8)BINOL-amine compounds are investigated. It is revealed that the intramolecular hydrogen bonds of these compounds contribute to the shift of the emission of their H(8)BINOL unit to a much longer wavelength. That is, the emission of H(8)BINOL is at λ = 323 nm, but that of the H(8)BINOL-amino alcohol (S)-5 is at λ = 390 nm. Binding of (S)-5 with mandelic acid suppresses its intramolecular hydrogen bonding and restores the short wavelength emission of the H(8)BINOL unit. When (S)-5 (1.0 × 10(-4) in CH(2)Cl(2)) was treated with (R)-mandelic acid (4.0 × 10(-3)), a large fluorescence enhancement at the short wavelength (λ(emi) = 330 nm) was observed with I(R)/I(0) = 11.7. When (S)-MA was used under the same conditions, the enhancement at the short wavelength emission was much smaller. Thus, a good enantioselective fluorescent response was observed with ef =3.5 ef: enantioselective fluorescence enhancement ratio = (I(R) - I(0))/(I(S) - I(0))]. This study demonstrates that the H(8)BINOL-based molecules are promising as a new class of enantioselective fluorescent sensors.