Self-assembled coordination cages based on banana-shaped ligands

Abstract

The combination of pyridyl ligands and square-planar Pd(ii) or Pt(ii) cations has proven to be a very reliable recipe for the realization of supramolecular self-assemblies. This tutorial review deals with the design, synthesis and host-guest chemistry of discrete coordination cages built according to this strategy. The focus is set on structures obeying the formula [PdnL2n] (n = 2-4). The most discussed ligands are bent, bis-monodentate bridges having their two donor sites pointing in the same direction. The structures of the resulting cages range from simple globules over intertwined knots to interpenetrated dimers featuring three small pockets instead of one large cavity. The cages have large openings that allow small guest molecules to enter and leave the cavities. Most structures are cationic and thus favour the uptake of anionic guests. Some examples of host-guest complexes are discussed with emphasis on coencapsulation and allosteric binding phenomena. Aside from cages in which the ligands have only a structural role, some examples of functional ligands based on photo- and redox-active backbones are presented.

Controllable Coordination Self‐Assembly Based on Flexible Tripodal Ligands: From Finite Metallocages to Infinite Polycatenanes Step by Step

“…Many research groups, such as those of Raymond, [5] Mirkin, [7] Amouri, [12] Clever, [13] Ward, [14] Hardie, [16] Atwood, [19] and others, [22][23][24][25] As we described in Scheme 1 (1), reactions of two-coordinated metal species and flexible tripodal ligands with a single donor site usually lead to M 3 L 2 metallocages. Only a few metal ions such as Ag 1 are naturally two-coordinated, and transitionmetal ions are normally six-or four-coordinated.…”

Adaptive self-assembly and induced-fit transformations of anion-binding metal-organic macrocycles

“…Coordination-driven self-assembly has become one of the most convenient strategies for the bottom-up construction of functional molecular ensembles12345. On the basis of elaborate symmetry considerations, numerous two-dimensional (2D) and three-dimensional (3D) architectures have been obtained in ease by the simple combination of designed ligands (L) and metal ions (M), which show great potential in the modulation of reactivity and/or photoelectric properties of guest molecules by encapsulation678910.…”

Assembled molecular face-rotating polyhedra to transfer chirality from two to three dimensions

“…Most of these polyhedra are highly symmetric and achiral202122232425, and chiral molecular polyhedra with lower symmetry have attracted more and more attention because they increase the complexity of motifs and may bring more sophisticated functions262728293031. Generally, the construction of chiral molecular polyhedra follows two strategies: to use predetermined 3D chiral building blocks as the edges3032, vertices3334 or faces3536 of polyhedra to transfer 3D chirality of the components to the 3D chirality of the chiral structures, or to use achiral components to generate chiral metal-organic polyhedra373839404142 during a self-assembly process. The latter approach relates to symmetry breaking, and investigation of the process of such complex molecular self-assembly may help to elucidate the evolution of matter towards complexity43.…”