Salen-Based Chiral Fluorescence Polymer Sensor for Enantioselective Recognition of α-Hydroxyl Carboxylic Acids

Abstract

(R,R)-Salen-based chiral polymer P-1 was synthesized by the polymerization of 5,5'-((2,5-dibutoxy-1,4-phenylene)bis(ethyne-2,1-diyl))bis(2-hydroxy-3-(piperidin-1-ylmethyl) benzaldehyde (M-1) with (1R,2R)-cyclohexane-1,2-diamine (M-2) via nucleophilic addition- elimination reaction, and (R,R)-salan-based polymer P-2 could be obtained by the reduction reaction of P-1 with NaBH(4). (R,R)-Salen-based chiral polymer P-1 can exhibit greater fluorescence enhancement response toward (l)-α-hydroxyl carboxylic acids, and the value of enantiomeric fluorescence difference ratio (ef) can reach as high as 8.41 for mandelic acid and 6.55 for lactic acid. On the contrary, (R,R)-salan-based chiral polymer P-2 shows obvious fluorescence quenching response toward α-hydroxyl carboxylic acids. Most importantly, (R,R)-salen-based polymer P-1 can display bright blue fluorescence color change in the presence of (l)-α-hydroxyl carboxylic acids under a commercially available UV lamp, which can be clearly observed by the naked eyes.

Metal Salen- and Salphen-Containing Organic Polymers: Synthesis and Applications

“…For instance, for mandelic acid an enantiomeric fluorescence difference ratio (ef) 142 of up to 8.41 in preference to the (L)enantiomer was found (Figure 8). 143 When reduced to the corresponding salan polymer, a "turn-off" of the fluorescence was observed, proving again that minor structural changes in the polymeric backbone can tune the corresponding properties dramatically.…”

“…Inset: photographic images of solutions of P1 (left), P1 with (D)-mandelic acid (middle), and P1 with (L)-mandelic acid in toluene/DME. 143…”

Solvent polarity effects on supramolecular chirality of a polyfluorene‐thiophene copolymer

“…These chiral polymers are promising candidates for a wide range of applications, including organic optoelectronic devices, photoswitching, chiral sensors, and chiral columns. [1][2][3][4][5][6] In particular, chiral columns have attracted attention as a key technology to separate enantiomers in response to the new physiological discoveries. 7 Valuable physiologically active substances usually possess multiple chiral centers in their molecular structure, thereby making the separation of a target enantiomer difficult.…”

“…Conjugated polymers bearing chiral substituents are known for their unique supramolecular chirality, which is evidenced in chiroptical properties such as circular dichroism (CD) and circularly polarized luminescence. These chiral polymers are promising candidates for a wide range of applications, including organic optoelectronic devices, photoswitching, chiral sensors, and chiral columns . In particular, chiral columns have attracted attention as a key technology to separate enantiomers in response to the new physiological discoveries .…”

Chiral fluorescence polyethers based on BINOL for enantioselective recognition of phenylalanine anion

“…[27][28][29][30][31] Chiral polymers used as fluorescence-based sensors for enantioselective recognition of chiral molecules offer several advantages over small molecule sensors, such as fluorescence efficiency enhancement and possible cooperative effects of multiple chiral units. [32][33][34][35] In this work, we synthesized a series of polyethers derived from chiral BINOL and optical epichlorohydrin. The BINOL plays the role of fluorophore, scaffold and the chiral center.…”