Actuated Conformational Switching in a Single Crystal of a Homodithiacalix[4]arene

Solution-mediated and single-crystal to single-crystal transformations of cucurbit[6]uril host–guest complexes with dopamine

The structural transformations of cucurbit[6]uril–dopamine complexes are associated with loss of water molecules either from the macrocyclic cavity or from the crystal lattice.

Synthesis and post-functionalization of alternate-linked-meta-para-[2 n .1 n ]thiacyclophanes

In recent decades, considerable research attention has been devoted to new synthetic procedures for thiacyclophanes. Thiacyclophanes are widely used as host molecules for the molecular recognition of organic compounds as well as metals. Herein, we report the selective and high-yielding synthesis of novel alternate-linked-meta-para-thiacyclophanes. These novel thiacyclophanes are selectively synthesized in high-yielding procedures. Furthermore, post-functionalization of the phenolic moieties was successfully performed. The 3D structure of the alternate-linked-meta-para-[2².1²]thiacyclophane was further elucidated via X-ray crystallographic analysis.

Fixing the Conformation of Calix[4]arenes: When Are Three Carbons Not Enough?

Calix[4]arenes are unique macrocycles that through judicious functionalisation at the lower rim can be either fixed in one of four conformations or remain conformationally flexible. Introduction of propynyl or propenyl groups unexpectedly provides a new possibility; a unidirectional conformational switch, with the 1,3-alternate and 1,2-alternate conformers switching to the partial cone conformation, whilst the cone conformation is unchanged, under standard experimental conditions. Using ¹ H NMR kinetic studies, rates of switching have been shown to be dependent on the starting conformation, upper-rim substituent, where reduction in bulk enables faster switching, solvent and temperature with 1,2-alternate conformations switching fastest. Ab initio calculations (DFT) confirmed the relative stabilities of the conformations and point towards the partial cone conformer being the most stable of the four. The potential impact on synthesis through the "click" reaction has been investigated and found not to be significant.

Glutathione-responsive homodithiacalix[4]arene-based nanoparticles for selective intracellular drug delivery

Glutathione-responsive, paclitaxel-loaded nanoparticles based on homodithiacalix[4]arene were successfully developed, exhibiting selective drug release in cancer cells.

Chiral metal-macrocycle frameworks: supramolecular chirality induction and helicity inversion of the helical macrocyclic structures

Porous molecular solids composed of discrete macrocycles/cages have great potential for catalysis, separation and sensing techniques. Dynamic structural transformation of the host building blocks, especially a helicity inversion responsive to chemical triggers, is central to upgrading the spatial functions. Here we have achieved the syntheses of homochiral porous molecular solids composed of helical metal macrocycles through supramolecular chirality induction to both enantiomorphic forms with the aid of two different enantiopure sugar-derived lactones in the crystallization process. Moreover, we found that the helicity of the macrocyclic skeletons can be inverted in the crystalline state only by changing the type of solvent. This finding would lead to dynamic control of space chirality in connection with optical resolution, chiral amplification and asymmetric reactions.

Solvent diffusion through a non-porous crystal ‘caught in the act’ and related single-crystal-to-single-crystal transformations in a cationic dinuclear Ag(i) complex

A few snapshots of a dynamic solvent diffusion process through a seemingly non-porous crystal of a dinuclear, cyclic Ag(i) complex were revealed. These indicate the complexity of the process, which involves not only relocation of the molecules in the crystal lattice, but also conformational adjustments of the metallocycles in response to solvent uptake/release.

A metal-free three-component reaction for the regioselective synthesis of 1,4,5-trisubstituted 1,2,3-triazoles

A metal-free three-component reaction to synthesize 1,4,5-trisubstituted 1,2,3-triazoles from readily available building blocks, such as aldehydes, nitroalkanes, and organic azides, is described. The process is enabled by an organocatalyzed Knoevenagel condensation of the formyl group with the nitro compound, which is followed by the 1,3-dipolar cycloaddition of the azide to the activated alkene. The reaction features an excellent substrate scope, and the products are obtained with high yield and regioselectivity. This method can be utilized for the synthesis of fused triazole heterocycles and materials with several triazole moieties.