Helicity Control of Triphenylamine‐Based Supramolecular Polymers: Correlation between Solvent Properties and Helicity in Supramolecular Gels

Abstract

We describe the role of amide groups formed by achiral and chiral moieties to study supramolecular helicity at the molecular level and the correlation between helicity and solvent properties at the supramolecular level. Using circular dichroism (CD) spectroscopy, we observed the CD spectra of supramolecular gel 1, which comprised a triphenylamine (TPA) core, terpyridine, and alanine moieties, formed in various solvents. The strong positive CD signals of supramolecular gel 1 formed in organic solvents, such as chloroform, tetrahydrofuran (THF), and dichloromethane, which have low polarity and a low acceptor number, were observed at 350 nm, indicating right-handed helicity. In contrast, the negative CD signals of supramolecular gel 1 formed in mixed DMSO/water (5:1 v/v), methanol, ethanol, and n-propanol were obtained at 350 nm, indicating left-handed helicity. These findings suggest that the helicity of supramolecular gel 1 was strongly influenced by the solvent properties. Indeed, atomic force spectroscopy images showed the right- and left-handed helicity of supramolecular gel 1 formed in various organic solvents, which was pure helicity.

Solute–Solvent Interactions in Modern Physical Organic Chemistry: Supramolecular Polymers as a Muse

“…In these least polar solvents, the increased favorability of the elongation pathway leads to long fibers, rather than circular polymers. The morphological changes of supramolecular polymers upon changing solvents, highlighted by the above examples, have also been observed in triarylamines, , metallosupramolecular polymers, , azobenzenes, and pyrenes, showing that pathway selection through solvent effects is a general phenomenon in supramolecular polymerizations.…”

Triarylamine-Based Supramolecular Polymers: Structures, Dynamics, and Functions

“…26 Recently, based on the demonstrated helical nature of the TATA stacks, 5 a number of mechanistic studies related to their supramolecular polymerization were published by several research groups. 6,8,23,[27][28][29][30][31] For instance, by adding chiral side chains to the TATA core, Miyajima and Aida demonstrated the possibility to control the M or P helicity of the corresponding supramolecular polymers, and further to fully bias the handedness of a racemate of supramolecular helices made of TATA having no chiral side chains by using only 0.2 mol% of enantiopure TATA (Figure 3B). 6 The control of 500 soldiers by only 1 sergeant represents an unusually strong amplification of chirality attributed to the peculiar dynamics of the TATA propellers.…”

“…The sensitivity of chiral TATA derivatives to environmental parameters was also nicely demonstrated by Jung and collaborators, who have revealed correlations between solvent properties and the selective expression of either left-handed or right-handed helicities in organogels. 27 Interestingly, Kim and collaborators published a study in which they observed a full control on the supramolecular chirality of TATA helices by simply using visible circularly polarized light (CPL). 23 Indeed, irradiation of TATA in chlorinated solvents with r-or l-CPL induces their self-assembly with opposite chirality, and moreover the resulting handedness could be totally switched by irradiating with a CPL of the opposite rotational direction (Figure 3C).…”

Covalently Trapped Triarylamine‐Based Supramolecular Polymers

“…The presence of well‐defined bands at 3290 and 1650 cm −1 are characteristic of hydrogen‐bonded N−H and C=O stretching bands, respectively. In addition, their high symmetry suggests a three‐fold helical arrangement of the molecules with intermolecular hydrogen bonds between adjacent TATA cores, as previously described for such compounds in the literature . Above the onset gelation concentration, the morphology of the individual fibers in the physical gel (15 m m in toluene; hereafter referred to as sample A) was found to be similar to those probed from solutions, as observed for instance by SEM imaging of the corresponding aerogel (Figure c).…”