Herringbone Helical Foldamers from Aromatic Ether Derived ϵ-Amino Acid Peptides

Oligomers based on an aromatic ether derived ϵ-amino acid peptides folded into herringbone helical structures, induced by successive NH-O-NH & O-NH-O bifurcated hydrogen bonding interactions and reinforced by π-π stacking between aryls from adjacent layers. The diaryl ether bonds -O- worked both as structural units to provide turn motifs for changing the amplitude of the slope along the axis of helix for herringbone formation, and also as acceptors for hydrogen bonding. Attachment of a single chiral carbon to the C-termini of the peptides induced excess of single-handed screw sense and amplification through the chain propagation as exemplified by chain length dependent circular dichroism (CD) investigations.

Synthesis, structure, and anion binding of functional oxacalix[4]arenes

Oxacalix[4]arenes obtained from the highly efficient, one-pot S_NAr reaction were post-macrocyclization functionalized through the reduction of nitro groups and hydrolysis of the ester groups to obtain several derivatives of desired solubility. The difficulties in basic hydrolysis of ester groups were overcome via developing an acid hydrolysis method for tert-butyl ester derivatives of this class. The synthesis of symmetrical oxacalix[4]arenes from an unsymmetrically substituted precursor was also explored via a multiple step fragment coupling approach. Compounds 17 & 18 adopted 1,3-alternate conformations in the solid state as most oxacalix[4]arenes did, and a chair (zigzag) conformation was revealed for tetraamido oxacalix[4]arene (6a) by X-ray single crystal analysis. The tetraureido oxacalixarene (7) showed strong association towards various anions such as F^-, Cl^-, Br^-, I^-, Ac^-, and HSO₄^- with a 1 : 1 stoichiometry as revealed by ¹H NMR analysis and UV-vis measurements.

Novel oxacalix[2]arene[2]triazines with thermally activated delayed fluorescence and aggregation-induced emission properties

New kinds of oxacalixarenes based on the triazine moiety have been synthesized, which showed highly twisted conformations and small ΔEST, as well as temperature-dependent transient PL decay curves, indicating the excellent thermally activated delayed fluorescence properties. Moreover, the oxacalixarenes also exhibited apparent aggregation-induced emission properties in THF/H2O mixtures.

Synthesis and Structures of Triptycene-Derived Oxacalixarenes with Expanded Cavities: Tunable and Switchable Complexation towards Bipyridinium Salts

New triptycene-derived oxacalixarene H1 was efficiently synthesized by a template cyclization step, and anilino-substituted macrocycle H2 was subsequently afforded through straightforward nucleophilic displacement of the active chlorine atom in H1. Oxacalixarene H1 adopts a fixed boat-like 1,3-alternate conformation and shows moderate complexation abilities towards various bipyridinium salts. However, the affinities of H2 towards the guests were found to be substantially stronger, which could be tentatively attributed to the additional hydrogen-bonding site, π-π stacking site, and especially the increased electron richness of the host. Furthermore, the acid-base switchable complexation process between H1 and the bipyridinium salt was also realized, which could potentially facilitate the construction of high-level stimuli-responsive supramolecular structures based on the newly synthesized oxacalixarene.

Azacalix[2]arene[2]carbazoles: synthesis, structure and properties

A new type of –NH– bridged azacalix[2]arene[2]carbazoles has been synthesized by aromatic nucleophilic substitution reactionviaone pot and/or fragment coupling strategy.