Metallosupramolecular cages: from design principles and characterisation techniques to applications

Abstract

This Tutorial Review discusses the principles and techniques behind the design, characterisation and applications of metallosupramolecular cages.

Directing metallo-supramolecular assembly through complementarity

“…1b). 4 This has the advantage of synthetic ease when the system is well designed, and architectures of impressive size [5][6][7][8][9] have been generated in this fashion. However, reaction products able to be controllably formed have tended to be high in symmetry and therefore lacking in the structural (and thereby functional) complexity so evident in nature.…”

Water-Soluble Self-Assembled Cage with Triangular Metal–Metal-Bonded Units Enabling the Sequential Selective Separation of Alkanes and Isomeric Molecules

“…Since the first serendipitous isolation of a self-assembled tetrahedral coordination cage, the development of discrete three-dimensional (3D) coordination cages, − especially water-soluble molecular cages comprising accessible cavities, has attracted a great deal of research attention. − Such molecular cages adopt different geometries and include accessible hydrophobic inner spaces; indeed, these species have found widespread use in the selective encapsulation, separation, and release of a variety of guest molecules, as well as in the promotion of chemical reactions in the aqueous phase. − The design and development of new systems that can distinguish between structurally similar compounds would provide new applications for self-assembled tetrahedral coordination cages, especially in the context of the separation of isomeric molecules.…”

Spin Crossover Induced By Changing the Identity Of the Secondary Metal Species In A Face-Centred FeII8NiII6 Cubic Cage

“…The design and assembly of discrete polynuclear materials that incorporate an internal cavity remains an active goal in metallo-supramolecular chemistry. 1,2 Such molecules have shown potential in a range of future applications which take advantage of host-guest interactions, including sensing, 3-6 catalysis, [7][8][9][10] drug encapulation 11,12 and the selective uptake of guest molecules [13][14][15][16] . In addition, there has been continuing interest in the construction of new cage systems as photoactive [17][18][19] and magnetic materials, 20 with the latter including spin crossover (SCO) systems.…”

“…Currently, there exists a vast structural diversity of metallo-organic cages, owing to the development of multiple synthetic strategies that frequently involve metal-directed selfassembly. 1,2,[43][44][45] One widely employed strategy is the metalloligand approach. 23,[46][47][48][49][50][51][52][53][54] Variation of the nature of metal ions and ligand scaffold can direct cage assembly, and has resulted in the generation of a variety of cage topologies, motivated by the search for increased functionality and complexity 55 .…”

“…This structure remained high spin at the Fe(II) centres even to low temperatures, with no SCO observed. In this study, we present an analogous structure, that differs in the identity of the facial bridging metal, in this case Ni(II), forming a [Fe8Ni6L8(CH3CN)12] 28+ heterometallic cubic cage, (1). Remarkably, simply by changing the identity of the square planar four coordinate Pd(II) to the distorted octahedral six coordinate Ni(II) metal centre, complete and incomplete SCO was observed through crystallographic and magnetic susceptibility measurements respectively, owing to the degree of solvation.…”