Strategies to synthesize a chiral helical polymer accompanying with two stereogenic centers for chiral electroanalysis

Abstract

In most cases, the recognition efficiency of chiral electroanalysis relies on the chiral carbon center, whereas its medium is just used to transfer the electron. Differently, in this study, an ionic helical polymer with right- or left-handed configuration was prepared via an acid-base interaction between the ionic polymer and enantiopure 1,2-diphenylethane-1,2-diamine. The structure and absolute handedness of the helical polymers were well characterized by the circular dichroism spectrum, gel permeation chromatography, and Fourier transform infrared spectroscopy. The pyridinium moiety of the helical polymer contributes to the electron transfer when it was directly modified on the surface of the glassy carbon electrode as an electrochemical enantioselector for chiral electroanalysis. Results indicated that different configurations of amino acids can be recognized in the responses of different electric signals, namely peak current or peak potential. The peak current ratio between L- and d-isomer can be up to 7.5 and 23.2 for tryptophan and tyrosine, respectively. Most importantly, the reversal of the electric signal can be observed toward L- and d-isomer under the different testing conditions such as pH and metal ion content, because of two stereogenic centers (the chiral inducer and the stereogenic axis) in the helical polymer. Overall, we believe that the present study offers a great promise for the synthesis and application of the ionic helical polymers accompanying with multiple stereogenic centers.