Chemical Transformations in Confined Space of Coordination Architectures

Abstract

The scholastic significance of supramolecular chemistry continues to grow with the recent development of catalytic transformations in confined space of supramolecular architectures. It has come a long way from a natural cavity containing molecules to modern smart materials capable of manipulating reaction pathways. The rise of self-assembled coordination complexes provided a diverse array of host structures. Starting from purely organic compounds to metalloligand surrogates, supramolecular host cavities were tuned according to the requirement of the reactions. The understanding of their participation in a reaction led to better usage of those assemblies for specific reaction sequences. Commencing from cyclodextrin, a wide range of organic molecules was used for cage-catalyzed organic transformations. However, difficulties in synthesis and a tedious purification procedure led chemists to choose a different pathway of metal-ligand coordination-driven self-assembly. The latter stood out as a potential replacement of the organic cages, overcoming the previous drawbacks. In the glut of different transition-metal assemblies used for catalytic transformations, many of them showed chemo- and stereoselective products. However, the small cavity size in some of them led to premature failure of the reaction. In that context, "molecular barrels" showed good efficacy for the catalytic reaction sequence. The large cavity size and bigger orifice for intake of the substrate and easy release of the product made them a better choice for catalysis. Additionally these are mostly used in aqueous media, which reinforces the idea of green and environmentally nonhazardous chemistry. In this Viewpoint, we discuss the use of metal-ligand coordination-driven self-assembled molecular containers used for catalysis with special emphasis on molecular barrels. This paper built on existing literature provides a thorough development of the fertile ground of the coordination architecture for catalysis and its future direction of propagation.

Better Together: Functional Heterobimetallic Macrocyclic and Cage‐like Assemblies

“…An impressivea pplication of metallosupramolecular cages is the use as molecular flasks or even supramolecular catalysts. [92] Mimicking am ain functiono fe nzymes,s uch applicationsa re of major interest, but likewise difficult to achieve. Still, there are some fascinating examples of heterobimetallic cages that are capable of mediating organic reactions within their cavities.…”

Structural and Dynamic Aspects of Palladium(II)‐Based Self‐Assembled Binuclear Coordination Complexes

“…The Pd 2 L' 2 L 2 and Pd 2 L 4 compositions of the complexes 1 and 2 a in the solution state were further supported by electrospray ionization mass spectrometry (ESI-MS). The mass spectrum of 1 showed isotopic peak patterns at m/z = 330.6079 and 461.4727 corresponding to the ions 4…”

“…[15] Electrostatic interactions of the anions with the cage units could be observed in the packing diagram. One exohedral unit of PF 6 anion is sandwiched between the metal centers of two cages in a one-dimensional network of {-[(PF 6 ) 2 &Pd(L) 4 Pd]-F(PF 4 )F-[(PF 6 ) 2 &Pd(L) 4 Pd]-F(PF 4 )F-} n (PF 6 ) 2n type situation ( Figure 5). The non-bonded Pd-Pd axis of all the cages of the one-dimensional chain are found to be collinear so also the bound F-P-F part of the sandwiched anionic units.…”

“…Thus, simple elongation of the concerned organic ligands allow the enlargement of the endohedral space of a given cage . Cage molecules with large cavities are well explored for molecular recognition, supramolecular catalysis, stabilization of reactive species, biomedical applications and so on. Incorporation of lengthy spacers in ligand back‐bone is thus a prime requirement to prepare coordination cages with larger cavities.…”

Highly Stable Copper(I)–Thiacalix[4]arene‐Based Frameworks for Highly Efficient Catalysis of Click Reactions in Water

“…Generally, organic ligands play an important role in the rational construction of MOF catalysts featuring tunable structures . Calix[4]arenes, as one type of excellent candidate ligand, have attracted considerable attention from researchers due to the ease of modifying their upper and lower edges .…”