Chiral fluorescent sensors based on cellulose derivatives bearing terthienyl pendants

Abstract

Chiral fluorescent sensors were designed and synthesized from naturally occurring optically active cellulose, in which a terthienyl moiety was used as a fluorescent signaling unit, and their chiral recognition abilities were investigated on the basis of an enantioselective fluorescence response to aromatic nitro compounds as quenchers. A cellulose phenylcarbamate derivative (Ce-1b) exhibited an apparent enantioselectivity for various types of aromatic nitro compounds containing either central or axial chirality. Considering the fact that a corresponding monosaccharide derivative showed almost no enantioselectivity, the chiral recognition ability of the cellulose-based fluorescence sensor is attributed to its regular higherorder structures, probably a one-handed helical conformation. The resolution ability of Ce-1b as a chiral stationary phase for high-performance liquid chromatography was basically higher than that of the previously reported cellulose tris( phenylcarbamate), revealing that the terthienyl-based pendant provides attractive chiral recognition sites along the helical backbone as well as the fluorescent functionality. † Electronic supplementary information (ESI) available. See

Development of Amylose- and β-Cyclodextrin-Based Chiral Fluorescent Sensors Bearing Terthienyl Pendants

“…Am- 1b and CyD- 1b exhibited fluorescence quantum yields of 5% and 6%, respectively, in THF and 2% and 3%, respectively, in hexane/THF (90/10, v / v ), which are low but sufficient for use as fluorescent sensor materials. As was the case for Ce- 1b [13], the fluorescence intensities of the present fluorophores were diminished when nitrobenzene ( 5 ) was added to the solutions (Figure S4). This was most likely as a result of photoinduced electron transfer from the fluorescent pendant residues to 5 .…”

“…An apparent split-type CD absorption was observed in the absorption region of the terthienyl pendant of Am- 1b (330–460 nm). As the previously reported glucose derivative Gl- 1b showed a very weak CD absorption in this region [13], the CD absorption of Am- 1b is considered to not be derived from the central chirality of the glucose ring. An asymmetric arrangement is most likely induced in the pendants of Am- 1b owing to the helical structure of the amylose phenylcarbamate framework, which is known to have a left-handed 4/3 helical conformation [18,19].…”

“…The amylose derivative (Am- 1b ) bearing fluorescent terthienyl-based π-conjugated pendants at the 2-, 3- and 6-positions of the glucose unit was synthesized according to our previously reported procedure (Scheme 1) [13]. Am- 1b showed good solubility, not only in common organic solvents, such as tetrahydrofuran (THF) and chloroform but also in mixtures of these solvents with 90 vol % hexane.…”

“…We have reported functionalized polysaccharide derivatives bearing reactive prochiral units or catalytically active sites as pendant groups with the aim of developing chiral auxiliaries or asymmetric catalysts, respectively, for asymmetric synthesis [11,12]. In addition, a cellulose-based chiral fluorescent sensor (Ce- 1b in Figure 1) containing a terthienyl moiety as a fluorescent signaling unit has also been developed and was found to show apparent enantioselectivity for various types of chiral compounds containing either central or axial chirality [13]. The significant contribution of the helical chirality of Ce- 1b to the chiral fluorescence sensing was demonstrated by the fact that the corresponding monosaccharide-based model compound (Gl- 1b in Figure 1) showed almost no enantioselectivity.…”

Fluorescence Sensing with Cellulose‐Based Materials

“…Ikai et al . have reported a chiral fluorescence sensor, designed and synthesized from naturally occurring optically active cellulose.…”