Potential‐Driven Chirality Manifestations and Impressive Enantioselectivity by Inherently Chiral Electroactive Organic Films

Abstract

The typical design of chiral electroactive materials involves attaching chiral pendants to an electroactive polyconjugated backbone and generally results in modest chirality manifestations. Discussed herein are electroactive chiral poly-heterocycles, where chirality is not external to the electroactive backbone but inherent to it, and results from a torsion generated by the periodic presence of atropisomeric, conjugatively active biheteroaromatic scaffolds, (3,3'-bithianaphthene). As the stereogenic element coincides with the electroactive one, films of impressive chiroptical activity and outstanding enantiodiscrimination properties are obtained. Moreover, chirality manifestations can be finely and reversibly tuned by the electric potential, as progressive injection of holes forces the two thianaphthene rings to co-planarize to favor delocalization. Such deformations, revealed by CD spectroelectrochemistry, are elastic and reversible, thus suggesting a breathing system.

Electrochemistry and Chirality in Bibenzimidazole Systems

“…To perform a preliminary enantioselectivity test of the new 1,1'-bibenzimidazolium salts, Performing the same electrooligomerization with enantiopure (R)-BT 2 T 4 in the absence of additives, the process is slower with respect to the racemate case (consistently with previous observations [7], and possibly as a consequence of the decrease in freedom degrees), and the CV pattern is more finely defined. However, both the oligomer oxidation onset and the maxima occur at potentials similar to those of the racemate, and again, the films are quite stable upon further cycling in monomer-free solution.…”

“…We have taken advantage of the biheteroaromatic strategy to prepare a successful modular series of chiral diphosphanes characterized by different phosphorous electronic availability and dihedral angle [6] and, very recently, electroactive oligothiophene macrocycles showing high chiroptical and enantiorecognition capacity [7][8][9][10][11].…”

“…The most satisfactory and promising functional materials we have prepared so far are based on electron-rich 3,3'-bithiophene [3,[7][8][9][10][11] or 2,2'-bipyrrole scaffolds [2,4,12], whereas electronpoorer biheteroaromatic units have shown modest performances [4].…”

“…we could perform preliminary enantiorecognition tests, employing them as additives in the electrooligomerization of chiral 2,2'-bis[2-(5,2'-bithienyl)]3,3'-bithianaphthene (BT 2 -T 4 ) monomer, both as enantiopure antipodes and as racemate [7][8][9][10][11] (Scheme 2).…”

Chirality in metals: An asymmetrical journey among advanced functional materials

“…Enantiospecific separations via chromatography or membranes, chiral heterogeneous catalysis, chiral electrodes and sensors are all in the scope of interest of pharmaceutical and agrochemical industries. [3][4][5] However, chirality is not only a property of crystals of homochiral organic molecules. Rather, the crystals of many inorganic materials are also chiral.…”