Synthesis And Properties Of Chiral Fluorescent Chemosensors

Fluorescent chemosensors are molecules whose fluorescence excitation/emission changes in response to the surrounding medium or through specific molecular recognition events. Due to their simplicity and high sensitivity, fluorescent sensors have been widely utilized as popular tools for trace ion recognition, biological molecule recognition and so on. Fluorescent chemosensors based on binaphthol and 8-hydroxyquinoline were synthesized. The responsive properties of the polymers on chiral molecules or the compounds on metal ions were investigated by fluorescent spectra.1. Synthesis of polymers based on binaphthol and their applications on chiral molecule recognitionThe chiral polymer P-1 incorporating (S)-2,2'-binaphthol (BINOL) and (S)-2,2'-binaphthyldiamine (BINAM) moieties in the main chain of the polymer backbone was synthesized by the polymerization of (S)-6,6'-dibutyl-3,3'-diformyl-2,2'-binaphthol (S-M-1) with (S)-2,2'-binaphthyl-diamine (S-M-2) via nucleophilic addition-elimination reaction, and the chiral polymer P-2 could be obtained by the reduction reaction of P-1 with NaBH4. The fluorescence intensity of the chiral polymer P-1 exhibits gradual enhancement upon addition of (D)-or (L)-phenylalaninol and keeps nearly a linear correlation with the concentration molar ratios of(D)-or (L)-phenylalaninol. The value of enantiomeric fluorescence difference ratio (ef) is 6.85 for the chiral polymer on (D)-phenylalaninol. On the contrary, the chiral polymer P-2 shows no obvious fluorescence response towards either (D)-or (L)-phenylalaninol.2. Synthesis of chiral compounds based on 8-hydroxyquinoline and their applications on metal ions recognitionComponds CS1, CS2, CS3 based on 8-hydroxyquinoline was synthesized. The responsive properties of CS1, CS2, CS3 on various metal ions(Zn2+, Na+, K+, Mg2+, Ca2+, Co2+, Ag+, Cd2+, Ni2+ and Pb2+) were investigated by fluorescent spectra. Compared with CS1 and CS2, chiral compound CS3 can show a pronounced fluorescence enhancement as high as 10-fold after the addition of leq Zn2+. The results indicate this kind of the compond CS3 based on 8-hydroxyquinoline as a receptor can exhibit high sensitivity and selectivity for Zn2+ recognition.