Study On The Interaction Between Saccharides And New Fluorescence Probes With ICT Behavior

Chapter 1: The basic structure and property of monosaccharide had been introduced and the mechanisms of the fluorescence probe containing boronic acid group for saccharides recognition were summarized. The recent development of the interactions between the compound containing boronic acid group and saccharides was described further. Chapter 2: P-(Diphenylamino) phenyl boronic (DPBA) as a novel type of fluorescent probe for monosaccharides have been studied by fluorescence spectroscopy. With increasing pH and adding of sugars, the form of boronic acid group was changed from the neutral form with sp~2 -hybridization to the anionic form with sp~3-hybridization. This change induced a blue shift of about 50 nm and a dramatic decrease of intensity in the emission spectrum of DPBA .The biding constants were obtained by fitting the titration curves against monosaccharides. The binding constants followed the order: D-Fructose (5264.5 ± 46.3L/mol)? D-Galactose(895.4 ± 27.7L/mol)>D-Mannose (689.6 ± 30.2L/mol) >Glucose(637.1 ±21.3 L/mol). The results suggest DPBA can be used to recongnized D-fructose with high selectivity .The intramolecular charge transfer (ICT) mechanism was employed.Chapter 3: A novel compound 4-(diphenylamino) biphenyl-4'-boronic acid (DBBA) was synthesized as a novel type of fluorescent probe for monosaccharides. The ability of DPBA to interact with gluctose, D-fructose, D-galactose and D-mannose was systematically investigated by steady-state fluorescence spectrum method. The effect of various monosaccharides (gluctose, D-fructose, D-galactose, D-mannose) concentration on the biding process was discussed in detail. The biding constants were obtained by fitting the titration curves against monosaccharides. The binding constants followed the order: D-Fructose (4291.6 ± 47.9 L/mol)>> D-Galactose(383.6 ± 6.9 L/mol) > D-Mannose(255.3 ± 5.5 L/mol) > Glucose (50.9 ± 1.0 L/mol). The intramolecular charge transfer (ICT) mechanism was employed. Chapter 4: The inclusion complexe of p-(diphenylamino) phenyl boronic acid (DPBA) with carboxymethyl-(3-Cyclodextrin (CM-p-CD) as a fluorescence probe for monosaccharides recognition in water has been designed. The fluorescence intensity of DPBA is enhanced by forming an inclusion complex of DPBA-CM-P-CD. The inclusion complexe DPBA-CM-(3-CD showed large spectral shifts in the emission wavelength and a significant intensity charge on binding saccharides. When D-Fructose interacted with DBBA-CM-P-C in water containing 1% ethanol, the emission maxima from 421nm shifts to 383nm(A?x=306nm). This phonomina can be explained by the intramolecular charge transfer (ICT) mechanism. The 1:1 binding constants obtained by fitting the titration curves against monosaccharides and the binding constants followed the order: D-Fructose (1714.2 ± 70.4 Lmol"')? D-Mannose(409.5±31.2 Lmol"1) > D-Galactose(292.6 ± 24.5Lmol'') = Glucose (221.9+ 15.2 L mol'1).Chapter 5: The interaction mechanisms of P-(Diphenylamino) phenyl boronic (DPBA) ^ 4-(diphenylamino) biphenyl-4'-boronic acid (DBBA) and DPBA- carboxymethyl-(3-Cyclodextrin with monosaccharides have been investigated briefly. The intramolecular charge transfer (ICT) mechanism was employed. Phenylboronic acids are weak Lewis acids with pKa. values ~9. Formation of a boronate ester via interaction with a monosaccharide increases the electrophilicity of the boron group, thereby reducing its pKa value to~6. At pH values between 6.5 and 8.5, the boronic acid exists in its neutral form;however, in the presence of a sugar, it exists in its anionic form. This change in the electronic properties of the boron group leads to the loss of ICT effect and results a blue shift and the change of the intensity.