Coordination chemistry in the solid state

Since the late 19th and early 20th centuries the coordination chemistry of complexes has been a central theme of inorganic chemistry. Werner's Nobel Prize-winning development of the field has been followed by many years of outstanding research. However, one of the most striking aspects of recent research in inorganic chemistry has been the explosion in interest in coordination chemistry in the solid state. Of course, this type of chemistry is not exclusively a recent phenomenon – solid state coordination polymers are known in the literature from at least the 1950s and probably before then – but the sheer volume of research effort in the last 20 years has been extraordinary, and the range of chemistry studied makes this area one of the most productive in the whole of chemistry.

Of course, much of this interest has been driven by the concept of ‘nodes and spacers’ developed by Robson in the early 1990s, which was then extended for the preparation of ‘superporous’ metal–organic frameworks, which have really excited the research community. However, the papers in this themed issue showcase the breadth of inorganic chemistry research that is ongoing around the world – there is high quality work on synthesis and gas adsorption, but this is augmented by some beautiful examples of new applications in wide range of areas, from luminescence to catalysis.

The synthesis of coordination polymers and metal–organic frameworks still makes up a substantial proportion of the field, and several of the papers in this issue highlight preparative techniques. Three Perspectives (DOI:10.1039/C2DT11989G, DOI:10.1039/C2DT12103D and DOI:10.1039/C2DT12006B) cover the areas from the use of porphyrin ligands in the solid-state, the use of sequential self-assembly and the current state-of-the-art in mechanistic aspects of how metal–organic framework crystals form. Unusual preparative methodologies, such as hydro-ionothermal (DOI:10.1039/C2DT11907B) or mechanochemical synthesis (DOI:10.1039/C2DT12012G), highlight how creative chemists can provide routes to novel solids showing interesting properties. Pingyun Feng and coworkers show in a ‘hot’ communication (DOI:10.1039/C1DT11975C) how lithium cubane clusters can be used to produce various different supramolecular coordination assemblies – a clever approach to the use of ‘designer’ secondary building units that is mirrored in several of the other contributions. In another ‘hot’ paper Barbour et al. describe examples of supramolecular isomorphism and solvatomorphism (DOI:10.1039/C1DT11564B).

A traditional area of strength for metal–organic frameworks in terms of their properties has been gas adsorption. Papers from Long (DOI:10.1039/C2DT12138G), Humphrey (DOI:10.1039/C2DT12011A), Li (DOI:10.1039/C2DT12301K) and others show how important gases such as hydrogen and carbon dioxide can be manipulated using porous coordination frameworks. However, it is striking how interest in other gases and vapours is rising, and in this issue there are papers on wide ranging topics such as ammonia adsorption (DOI:10.1039/C2DT11908K) and the delivery of biologically active hydrogen sulfide (DOI:10.1039/C2DT12069K). It is also very clear how important computer modelling and simulation are in this field, predicting the properties of solids and supporting experimental studies, and several contributions in the area of gas storage benefit from high quality simulations.

However, gas storage is far from the only potential application of coordination chemistry in the solid state. Properties such as luminescence (DOI:10.1039/C1DT11584G), magnetism (DOI:10.1039/C2DT12311H) and redox activity (DOI:10.1039/C2DT12304E) are all described in excellent papers, as are ligand field effects on the multiferroic behaviour of perovskite-like frameworks (DOI:10.1039/C2DT12300B). The growth of coordination-based solids on surfaces, like that described by Bein and co-workers (DOI:10.1039/C2DT12265K), offer new routes to devices and other functional solids with clear applicability. The field of composite solids is also represented, and the work by Bandosz shows how combining MOFs with graphite oxide can produce interesting new adsorbents, opening up many new avenues for novel solids with potentially useful applications (DOI:10.1039/C2DT12017H).

A particularly fertile area of current research is catalysis. There are many examples of excellent catalytic properties in the literature. In this issue, the groups of Corma (DOI:10.1039/C2DT1240G), Čejka (DOI:10.1039/C2DT11978A) and Farrusseng (DOI:10.1039/C2DT11994C) all show that coordination framework compounds can be used as catalysts, or modified to produce catalytically active solids. Such work is at the cutting edge of the field.

The theme that links all the papers published in this themed issue is the breadth and diversity of inorganic coordination chemistry that can be utilised to provide new solids with beautiful topologies and exciting chemical properties. The vitality of the field is demonstrated by the number of papers (>50) in this special issue and their extremely high quality. I would like to congratulate all the authors for their contributions, the work not only represents a collection of research that is at the forefront of the current field, but also acts as a signpost for those wishing to follow in their footsteps and make telling contributions to the area. Coordination chemistry in the solid state has a strong future, and I for one look forward to seeing the impact of the work reported in this special issue on forthcoming research.

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