Helical Inversion of Gel Fibrils by Elongation of Perfluoroalkyl Chains as Studied by Vibrational Circular Dichroism

Helicity control of a perfluorinated carbon chain within a chiral supramolecular cage monitored by VCD

Confinement within supramolecular systems is the leading technology to finely tune guest functional properties. In this communication we report the synthesis of a chiral supramolecular cage able to bias the helicity of a perfluorinated carbon chain hosted within the cage. We monitor the phenomenon of chiral induction by Vibrational Circular Dichroism (VCD) experiments complemented by DFT calculations over the possible conformers.

In Situ Supramolecular Gel Formed by Cyclohexane Diamine with Aldehyde Derivative

Low-molecular-weight gels have great potential for use in a variety of fields, including petrochemicals, healthcare, and tissue engineering. These supramolecular gels are frequently metastable, implying that their properties are kinetically controlled to some extent. Here, we report on the in situ supramolecular gel formation by mixing 1,3-cyclohexane diamine (1) and isocyanate derivative (2) without any catalysis at room temperature in various organic solvents. A mixture of building blocks 1 and 2 in various organic solvents, dichloromethane, tetrahydrofuran, chloroform, toluene, and 1,4-dioxane, resulted in the stable formation of supramolecular gel at room temperature within 60-100 s. This gel formation was caused by the generation of urea moieties, which allows for the formation of intermolecular hydrogen-bonding interactions via reactions 1 and 2. In situ supramolecular gels demonstrated a typical entangled fiber structure with a width of 600 nm and a length of several hundred μm. In addition, the supramolecular gels were thermally reversible by heating and cooling. The viscoelastic properties of supramolecular gels in strain and frequency sweets were enhanced by increasing the concentration of a mixed 1 and 2. Furthermore, the supramolecular gels displayed a thixotropic effect, indicating a thermally reversible gel.

Ala–Ala dipeptides with a semi-perfluoroalkyl chain: chirality driven molecular packing difference and self-assembly driven chiral transfer

The chirality of amino acids triggered the chiral molecular stacking of dipeptides and, eventually, transferred to the semi-perfluoroalkyl chain.

A new horizon for vibrational circular dichroism spectroscopy: a challenge for supramolecular chirality

The development of the solid state and time-step VCD methods opened a new horizon to reveal the mechanism of chirality amplification from microscopic to supramolecular scales.

Helicity of perfluoroalkyl chains controlled by the self-assembly of the Ala-Ala dipeptides

Four Ala-Ala dipeptides with a perfluoroalkyl chain at the N-terminal were synthesized. They were able to self-assemble into helical nanofibers and/or twisted nanobelts in a mixture of DMSO/H₂ O. The handedness of nanofibers and nanobelts was controlled by the chirality of the alanine at the N-terminal. The stacking handedness of the phenylene groups and the helicity of the perfluoroalkyl chain were studied using circular dichroism spectroscopy and vibrational circular dichroism, respectively. The chirality of the alanine at N-terminal controlled the stacking handedness of the neighboring phenylene groups. Moreover, due to the low potential barrier between M- and P-helices of the perfluorocarbon chain, the handedness of the organic self-assemblies eventually controlled the helicity of the perfluorocarbon chain. X-ray diffraction indicated that a lamellar structure was formed by the dimers of the dipeptides.

Stereochemical effects on dynamics in two-component systems of gelators with perfluoroalkyl and alkyl chains as revealed by vibrational circular dichroism

The VCD method was applied to the gelation processes of chiral two-component gel systems.

Aggregation-Induced Chirality: Twist and Stacking Handedness of the Biphenylene Groups of n-C12H25O-BP-CO-Ala-Ala Dipeptides

In mixtures of water and dimethyl sulfoxide, 4'-(n-dodecyloxy)-1,1'-biphenyl-4-carbonyl Ala-Ala dipeptides can self-assemble into tubular structures that are formed by coiled nanoribbons. The twist and stacking handedness of biphenylene groups were studied using circular dichroism and confirmed by theoretical chemical calculations. The handedness of the coiled nanoribbons and the stacking handedness of biphenylene groups are controlled by the chirality of alanine at the C-terminus, whereas the twist handedness of biphenylene groups is determined by the chirality of alanine at the N-terminus. ¹H NMR spectra indicated that the hydrogen bond formed by the N-H group of alanine at the N-terminus plays an important role in the formation of organic self-assemblies. On the basis of small-angle X-ray scattering characterization, a dimer structure was proposed to form through the terminal COOH groups.