Coordination Framework Topology: Influence of Using Multimodal Ligands
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This article describes the use of multimodal ligands in constructing solid-state molecular materials, in particular coordination frameworks. It will be demonstrated that such ligands have advantages over simpler, more traditional unimodal ligands in controlling the topology of coordination frameworks at the molecular level. This gives rise to the hope of a high degree of design of coordination frameworks for subsequent use as advanced materials.
The construction of crystal-engineered frameworks using either coordinative-bonding or hydrogen-bonding interactions is an extremely topical area of inorganic and materials chemistry. The strong interest in this area arises because the synthetic procedure used to construct these materials allows, in principle, a high degree of design. New materials with tunable properties have been developed from coordination frameworks over recent years and as synthetic procedures become more advanced so the properties of these materials become more highly evolved.
In particular, new framework materials with host–guest properties, similar to those observed with zeolites, have been reported. The potential advantage of using coordination frameworks is that the components of the framework, metal, ligand, and anion can be readily chosen and designed to allow specific manipulation of the dimensions and shape of channels or pores. Component design gives rise to not only shape-selective inclusion but also the possibility of chemoselectivity. Recent examples include very high methane adsorption within a coordination framework and also rare example of dioxygen adsorption in which the dimensions of the framework channels give rise to a highly ordered O2 array. Examples of new materials with interesting magnetic and nonlinear optical properties have also been reported. It is even possible to incorporate more than one of these properties within a single material and this gives rise to highly novel and advanced materials such as a nanoporous molecular magnet with reversible solvent-induced mechanical and magnetic properties and a coordination-framework-based material that exhibits coexisting ferromagnetism and metallic conductivity.