Supramolecular Chemistry: A Toolkit for Soft Functional Materials and Organic Particles

Abstract

Self-assembly has proven to be a powerful tool for the construction of complex superstructures. The assembly of monomers into supramolecular architectures via non-covalent interactions is chiefly directed by the molecular structures, their functional groups, and environmental conditions. The principal advantage of non-covalent interactions is reversibility, which allows the assembly of monomers into supramolecular structures in situ depending on the local conditions. In addition, the supramolecular approach provides a degree of control over self-assembly at the molecular level, thereby influencing the macroscopic level and facilitating tuning of the bulk material properties. This review discusses the meritorious examples of supramolecular materials constructed through the molecular assembly process, guided by the classical principles of supramolecular chemistry. Furthermore, this year (2017) marks the 50 th anniversary of supramolecular chemistry in honor of the first example of supramolecular structure reported by Charles J. Pedersen and the achievements in the area of supramolecular chemistry ever since.

A Versatile Approach to Dynamic Amide Bond Formation with Imine Nucleophiles

“…Our initial studies on this system probedt he reversibility in the reaction of N-benzyl substituted imine 1a with benzoyl chloride (2a). As has been previously noted, mixingt hese in CDCl 3 leads to the rapid build-up of amide 3aa within minutes at ambient temperature, as determined by 1 HNMR analysis (Figure 2a,b ). The product 3 reacts with water (see below), and its formation must be performed under anhydrous conditions (see SI for details).…”

The Power of the Mechanical Bond

“…Since the first demonstration of a [2]catenane by Wasserman in 1960 1 -wherein the ring components held together by very weak van der Walls forces, leading to a nearly statistical formation (0.0001% yield)-many synthetic strategies have been proposed for the preparation of mechanically interlocked, so-called ''chainlike'' molecules (MIMs). [2][3][4] Notably, the introduction of template-directed synthetic strategies involving metal coordination and donor-acceptor interactions was the turning point in the field of MIMs, which allowed the efficient and successful synthesis of various MIMs. The integration of switchable units into MIMs led to the development of so-called molecular switches and ma-chines, in which the direction of the movement of individual components is controlled and directed by the application of external stimuli.…”

“…In this issue of Chem, Stoddart and coworkers report efficient syntheses of a 12+ [3]catenane that contains three mechanically interlocked 4+ rings and a [5]catenane containing four 4+ charged rings mechanically interlocked around an 8+ charged ring despite the significant Coulombic repulsion between the components. The authors employed a radically templated synthesis approach that took advantage of the high affinity of in-situ-generated viologen radical dimers upon the reduction of viologen moieties by using Cu powder under an inert atmosphere.…”

“…More specifically, the authors took advantage of the threading of the CBPQT 4+ ring onto bis (azide)viologen (AV 2+ ) and bis(alkyne) viologen (HV 2+ ) under reductive conditions, leading to the formation of inclusion complexes of [AV ($+) <CBPTQ 2($+) ] and [HV ($+) <CBPTQ 2($+) ] by a mutual radical-radical recognition mechanism. After the click reaction between the azide and alkyne moieties of the thread components to form [3]-and [5]-catenanes in their radical cationic states, the subsequent oxidation under air or with the oxidant NOPF 6 led to overall yields of 41% or 36%, respectively. From a design perspective, the length of the alkyl chains on the thread component is carefully tailored (10 Å ) so they can encapsulate two CBPQT 4+ rings and interact efficiently in their radical cationic states in the 12+ charged [3] catenane.…”

“…After the click reaction between the azide and alkyne moieties of the thread components to form [3]-and [5]-catenanes in their radical cationic states, the subsequent oxidation under air or with the oxidant NOPF 6 led to overall yields of 41% or 36%, respectively. From a design perspective, the length of the alkyl chains on the thread component is carefully tailored (10 Å ) so they can encapsulate two CBPQT 4+ rings and interact efficiently in their radical cationic states in the 12+ charged [3] catenane. The formation of both the radical cation and the fully oxidized states was verified by single-crystal X-ray analysis, which clearly showed the formation of the [3]catenane.…”