Wavelength-ratiometric probes for saccharides based on donor–acceptor diphenylpolyenes

Abstract

The spectroscopic and photophysical properties of two donor-acceptor derivatives of 1,4diphenylbuta-1,3-diene and 1,6-diphenylhexa-1,3,5-diene are described. Both compound posses a dimethylamino and a boronic acid groups as electron-donor and electron-withdrawing groups, respectively. Solvent polarity effects on the steady-state and fluorescence intensity decay are presented and show the formation of an excited-state charge-transfer (CT) state for both compounds. The formation of the anionic form of the boronic acid group at high pH induces a blue shift and an increase of the intensity in the emission spectra for both compounds. These spectral changes are interpreted as the lost of the electron-withdrawing property of the anionic form of the boronic acid group. The observed pK a of both compounds is around 8.8 and decrease to ~6 and ~7 in presence of fructose and glucose, respectively. Both compounds display a decrease of the mean lifetime at higher pH. Effects of the sugars on the fluorescence spectra and fluorescence lifetimes are also presented. For both compounds, a blue shift and an increase of the intensity are observed. These spectral changes lead to a wavelength-ratiometric method for the sugar recognition and analysis. Titration curves against fructose, galactose and glucose and dissociation constants are presented. Both compounds show a higher affinity for fructose. The affinity decreases for galactose and for glucose, respectively. Sugar effects on the fluorescence intensity decay are also presented. Both compounds display a decrease of the mean lifetime after addition of sugar.

Wavelength–Ratiometric Probes for the Selective Detection of Fluoride Based on the 6-Aminoquinolinium Nucleus and Boronic Acid Moiety

“…The affinity of boronic acid for diols is well known [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27], hence for any fluoride sensor based on the boronic acid moiety, it is important to characterize the monosaccharide response. Subsequently, we tested the response of BAQBAs towards both glucose and fructose.…”

“…Since the boronic acid group also interacts with other strong bases such as hydroxyl ions [37], BAQBAs are likely to also have a pH dependent response, although at pH 7 such as in physiological fluids or waste waters, the interaction is low (the concentration of OH − = 10 −7 M) and environmental and physiological safeguard sensing applications do not experience notable pH changes. While the many boronic acid containing fluorophores that have been synthesized to date [21][22][23][24][25][26][27] and are likely to show a fluoride response, only a few will demonstrate spectral shifts and intensity changes, affording for ratiometric sensing, while even fewer will demonstrate an additional poor/non-sugar response. Further, BAQBAs offer the additional possibility of lifetime based halide sensing (collisional quenching).…”

“…In contrast, a greater electron deficient nitrogen center provides for a higher affinity for monosaccharides (data not shown) [36]. Hence our unique choice of backbone substituents affords a high fluoride affinity with relatively little sugar response, even in the case of fructose, which is wellknown to have a high boronic acid affinity [21][22][23][24][25][26][27]. In this paper we characterize the fluoride response of BAQBAs in the presence of potential interferences such as sugar and other halides and, also the response towards the halides.…”

“…Fluoride can be accurately determined using fluoride-ion selective electrodes [8], spectrophotometry [9], gas chromatography [10] and even colorimetrically using boronic acid chemistry [11,12], although such systems are poisoned by the presence of sugars such as by glucose or fructose. It is due to the well-known high affinity between diol containing compounds and the boronic acid moiety that has lead to the development of carbohydrate sensors [13][14][15][16][17][18][19] chromatographic materials [20] and many glucose sensors [21][22][23][24][25][26][27].…”

Ophthalmic Glucose Monitoring Using Disposable Contact Lenses—A Review

“…For the identification of suitable transduction elements, boronic acid has been known to have high affinity for diol-containing compounds such as carbohydrates [18][19][20] (Scheme 1), where the strong complexation has been used for the construction of carbohydrate sensors [21][22][23][24][25][26][27][28], transporters [29] and chromatographic materials [30]. Boronic acid compounds have also been used for the synthesis of glucose sensors [31][32][33][34][35][36], where we note the work of Shinkai [31,32] and Lakowicz [33][34][35][36] to name but just a few workers in this field.…”