Solvent-Dependent Self-Assembly and Crystal Structures of a Salen-Based Macrocycle

Nanoscale Crystalline Sheets and Vesicles Assembled from Nonplanar Cyclic π-Conjugated Molecules

A fundamental challenge in chemistry and materials science is to create new carbon nanomaterials by assembling structurally unique carbon building blocks, such as nonplanar π-conjugated cyclic molecules. However, self-assembly of such cyclic π-molecules to form organized nanostructures has been rarely explored despite intensive studies on their chemical synthesis. Here we synthesized a family of new cycloparaphenylenes and found that these fully hydrophobic and nonplanar cyclic π-molecules could self-assemble into structurally distinct two-dimensional crystalline multilayer nanosheets. Moreover, these crystalline multilayer nanosheets could overcome inherent rigidity to curve into closed crystalline vesicles in solution. These supramolecular assemblies show that the cyclic molecular scaffolds are homogeneously arranged on the surface of nanosheets and vesicles with their molecular isotropic x-y plane standing obliquely on the surface. These supramolecular architectures that combined exact crystalline order, orientation-specific arrangement of π-conjugated cycles, controllable morphology, uniform molecular pore, superior florescence quench ability, and photoluminescence are expected to give rise to a new class of functional materials displaying unique photonic, electronic, and biological functions.

Hollow and Solid Spheres Assembled from Functionalized Macrocycles Containing Adamantane

An adamantane-based macrocycle possessing eight hydroxyl groups (1) was synthesized, in which the macrocyclic framework comprises two disubstituted adamantane molecules bearing phenyl derivatives connected to two biphenylene spacers by oxygen atoms. Furthermore, functionalized macrocycles containing methyl (2) and methoxycarbonylmethyl (3) groups were prepared. From the X-ray crystallographic analysis, the backbone of the macrocycles in all crystals had a nearly hexagonal shape with a cavity and these macrocycles could be arranged into different tubular structures dependent on the substituents. In acetone, macrocycle (1) formed stable hollow spherical aggregates with multilayer membranes. In contrast, macrocycle (3) exhibited no production of self-assembled materials in chloroform. The addition of hexane into the solution caused the generation of solid spheres and their fused network aggregates, which were finally transformed into crystals owing to the solvent effects.

Solvent-Switched Schiff-Base Macrocycles: Self-Sorting and Self-Assembly-Dependent Unconventional Organic Particles

Organic reaction is a powerful and versatile tool for the creation of various new substrates and materials. However, there have been few reports of the direct fabrication of organic particles by organic reactions. Herein, we report that water as a co-solvent can efficiently switch a [2 + 2] macrocycle (3) to a [1 + 1] macrocycle (4) in a Schiff-base reaction from the same precursors at room temperature. Unexpectedly, a series of tunable organic micro/nanoparticles, including solid microspheres, core-shell spheres, and vesicles, could be directly precipitated in one-step from the reaction medium with high yield. X-ray structure analysis and other characterizations indicated that social self-sorting and narcissistic self-sorting of the macrocyclic frameworks of 3 and 4 through noncovalent interactions play crucial roles in the formation of such organic particles. Most interestingly, the facile and mild fabrication conditions of the particles allowed us to accurately and in situ monitor their intermediate formation by controlling the reaction time. This work thus provides an advancement of the fabrication of tunable organic particles.

Organic core-shell-shaped micro/nanoparticles from twisted macrocycles in Schiff base reaction

A series of organic core–shell-shaped micro/nanoparticles from twisted enantiomeric macrocycles could be obtained in Schiff base reaction with high yield at room temperature.

Functional self-assemblies derived from noncovalent interactions such as lipid vesicles and DNA chiral double helices are a typical feature of natural life activity. Because of this phenomenon, a self-assembly approach for various functional organic particles is a desirable objective in supramolecular chemistry. Here, we report the discovery of enantiomeric conformers from a twisted macrocyclic host (MH), which was obtained from an achiral precursor by Schiff base reaction. Further studies suggest that a series of unexpected and stable core–shell-based organic micro/nanospheres can be directly precipitated from a simple reaction solution with high yield. A single-crystal X-ray diffraction analysis of MH revealed that the unusual C–H···π interaction triggered self-assembly of the enantiomeric forms in the solid state plays an important role in the formation of the core–shell-shaped organic particles.

Towards stable porous crystalline phases of molecular belts

A chemical modification of a molecular belt (M1) renders the molecule (M2) into a stable supramolecular nanotube porous crystal.