Molecular Fire Quencher: Cage-shaped molecular assemblies can regulate the reactivity of smaller molecules trapped within them. Mal et al. (p. 1697 ) extend this approach to enable the protection of elemental white phosphorus (P ₄ ), a substance that rapidly ignites on contact with oxygen. The tetrahedral cages self-assemble in aqueous solution through coordination of six ligands to four iron ions, and efficiently capture phosphorus from a suspension. The water-soluble host-guest constructs were stable in air for at least 4 months, but released intact P ₄ rapidly on displacement by added benzene.

Over the last two decades the field of metallosupramolecular self-assembly has emerged as a promising research area for the development of intricate, three-dimensional structures of increasing complexity and functionality. The advent of this area of research has strongly benefited from design principles that considered the ligand geometry and metal coordination geometry, thus opening up routes towards rationally designed classical (Archimedean or Platonic) architectures. In this tutorial review, we will focus on more recent developments in the design and synthesis of three-dimensional suprastructures which have non-classical architectures (non-Archimedean/Platonic solids) and we will explicitly address the secondary effects responsible for their formation. Three classes of metallosupramolecular assemblies will be discussed: architectures formed through the combination of a single ligand and metal, heteroleptic structures and heterometallic structures. It is hoped that our exposition may suggest how different principles employed in these three classes of structures might be combined to create even greater complexity and potential for function.

Compartmentalization of the aqueous space within a cell is necessary for life. In similar fashion to the nanometer-scale compartments in living systems, synthetic water-soluble coordination cages (WSCCs) can isolate guest molecules and host chemical transformations. Such cages thus show promise in biological, medical, environmental, and industrial domains. This review highlights examples of three-dimensional synthetic WSCCs, offering perspectives so as to enhance their design and applications. Strategies are presented that address key challenges for the preparation of coordination cages that are soluble and stable in water. The peculiarities of guest binding in aqueous media are examined, highlighting amplified binding in water, changing guest properties, and the recognition of specific molecular targets. The properties of WSCC hosts associated with biomedical applications, and their use as vessels to carry out chemical reactions in water, are also presented. These examples sketch a blueprint for the preparation of new metal–organic containers for use in aqueous solution, as well as guidelines for the engineering of new applications in water.

This review discusses recent advances in the use of molecular containers in complex chemical systems, focusing on three aspects: host–guest behaviour, structural transformations and reactivity modulation.