Multivariate compositions of zinc halide dipyridyl-naphthalenediimide coordination polymers are shown to directly tune photochromic response through modification of halide lone pair-NDI LUMO overlap. Photochromic materials have attracted widespread attention for applications in data storage, sensing and catalysis among many others.1–7 Naphthalenediimides (NDIs) in particular are an extensively studied family of often photochromic compounds. This property arises from the NDI’s electron-poor aromatic core and a low-lying LUMO which makes them readily reduced to a radical anion (NDI˙−), a process which is usually accompanied by a change in colour of the NDI-containing material.8,9 In addition, NDIs are readily modified through synthetically facile substitution of functional motifs in their imide positions,10 or directly onto the naphthyl core.11 These qualities make NDIs a popular choice in constructing functional crystalline materials such as metal-organic frameworks (MOFs), hydrogen-bonded organic frameworks (HOFs) and simple cocrystals.12–14 Crystalline NDI containing materials are attractive as the crystal engineering approach can be employed to tune electron-donor to electron-acceptor interfaces, while crystallography can inform the researcher on the precise inter- or intramolecular interactions which may give rise to the formation of the aforementioned NDI radical species, something which can be more challenging in the solution phase.15–17 In addition, crystal packing (particularly through π-stacking) can stabilise organic radicals, something which is attractive both for the investigation of radical species, but also in applications.18,19 Notably for crystalline materials such as coordination polymers (CPs) or MOFs, a multivariate-MOF (MTV-MOF) or multivariate-CP (MTV-CP) approach can be exploited wherein the composition of different metals or ligands can be systematically varied within a single polymer to tune the properties of the material.20-

Far from being simply rigid, benign architectures, metal-organic frameworks (MOFs) exhibit diverse interactions with their interior environment. From developing crystal sponges to studying reactions in framework materials, the role of both supramolecular chemistry and framework structure is evident. We explore the role of supramolecular chemistry in determining framework…guest interactions and attempts to understand the dynamic behavior in MOFs, including attempts to control pore behavior through the incorporation of mechanically-interlocked molecules. Appreciating and understanding the role of supramolecular interactions and dynamic behavior in metal-organic frameworks emerge as important directions for the field.

Surface-confined synthesis provides alternative reaction pathways to those utilized within solution-phase chemistry and offers a route to extended molecular architectures with nanoscale dimensions and fascinating magnetic, electronic, and catalytic properties. However, these reaction pathways can be complex multistep processes, containing multiple reactive intermediates. Optimizing the selectivity and efficiency of such synthetic routes should be underpinned by detailed mechanistic insight, which requires submolecular spatial resolution in combination with details of chemical evolution throughout the reaction process. A key challenge is the application of an experimental methodology that allows in-depth study of multistep reactions. Here, we combine the spatial resolution of scanning tunneling microscopy with temperature-programmed photoelectron spectroscopies and present a comprehensive characterization of a multistep on-surface reaction utilizing a brominated porphyrin species. The porphyrin species employed is a highly functionalizable "molecular building block" from which nanostructured materials can be built, and within this work we identify key differences between the reaction on Cu(111) and Au(111). Intermolecular Ullmann-type coupling as well as intramolecular ring-closing and self-metalation are observed: specifically, on Au(111) we characterize self-metalation within covalently coupled assemblies of ring-closed TPP. Our results highlight the differing reactivity of Au(111) and Cu(111) and the strong influence of the substrate upon the reaction pathway and preferred products, and we provide spectroscopic and topographical characterization for all reaction steps.

Structural disorder can be used to tune the properties of functional materials and is an important tool that can be employed for the development of complex framework materials, such as metal-organic frameworks. Here we show the synthesis and structural characterization of a metal-organic framework, UoB-100(Dy). Average structure refinements indicate that the node is disordered between two orientations of the nonanuclear secondary building unit (SBU). By performing 3D diffuse scattering (DS) analysis and Monte Carlo (MC) simulations, we confirm the presence of strong correlations between the metal clusters of UoB-100(Dy). These nodes assemble into a complex nanodomain structure. Quantum mechanical calculations identify linker strain as the driving force behind the nanodomain structure. The implications of such a nanodomain structure for the magnetic, gas storage, and mechanical properties of lanthanide MOFs are discussed.

The electrochemical and spectroelectrochemical behaviour of metal-organic frameworks (MOFs) using a perylene diimide (PDI) based ligand is reported. Through suitable functionalisation, a PDI-based ligand is made soluble, allowing successful synthesis of two MOFs in combination with cobalt dicarboxylate paddlewheel secondary building units. Spectroelectrochemical techniques are used to probe the electrochemical and optical behaviour of the MOFs demonstrating that the properties of the perylene diimide are maintained by the MOF, facilitating electrochromic behaviour.

decade ago, Zaworotko and co-workers engaged the principles of crystal engineering to demonstrate that narrow-pore (<0.7 nm) coordination networks are ideal sorbent platforms for small-molecule sorbates. This approach transformed sorbent design for such separations and has provided several performance benchmarks in trace gas capture-enabled purifications.

Hydrogen-bonded organic frameworks (HOFs) undergo photoexcitation to form radical bearing materials.

The synthesis of charge assisted amidinium & ctdot;phosphonate hydrogen-bonded organic frameworks (HOFs) is reported. Two tectons, with either a biphenyl or naphthalene diimide backbone, were combined with bis-amidinium salts to afford HOF1 and HOF2, respectively. Whereas HOF1 formed rapidly, typically within two days of mixing, HOF2 proved more challenging to synthesise. Interestingly, the presence of sunlight facilitated the rapid formation of HOF2 within a few hours. Although crystals of tectons 1H4 or 2Et4 exhibited densely packed structures, combination of the corresponding phosphonate bases with bis-amidinium cations, through amidinium & ctdot;phosphonate interactions, gave open framework materials. The HOFs formed through this approach exhibited notable stability limitations, including a propensity for phase transformations or structural collapse upon solvent removal. Charge assisted amidinium & ctdot;phosphonate hydrogen-bonded organic frameworks (HOFs) are reported displaying a complex array of intermolecular interactions.

Metal--organic frameworks (MOFs) are a rapidly growing class of materials that offer great promise in various applications. However, the synthesis remains challenging: for example, a range of crystal structures can often be accessed from the same building blocks, which complicates the phase selectivity. Likewise, the high sensitivity to slight changes in synthesis conditions may cause reproducibility issues. This is crucial, as it hampers the research and commercialisation of affected MOFs. Here, we present the first-ever interlaboratory study of the synthetic reproducibility of two Zr--porphyrin MOFs, PCN-222 and PCN-224, to investigate the scope of this problem. For PCN-222, only one sample out of ten was phase pure and of the correct symmetry, while for PCN-224, three were phase pure, although none of these show the spatial linker order characteristic of PCN-224. Instead, these samples resemble dPCN-224 (disordered PCN-224), which was recently reported by us. The variability in thermal behaviour, defect content, and BET surface area of the synthesised samples are also studied. Our results have important ramifications for field of metal--organic frameworks and their crystallisation, by highlighting the synthetic challenges associated with a multi-variable synthesis space and flat energy landscapes characteristic of MOFs.

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Paul R. Raithby opened discussion of the paper by Maria Diaz Lopez: In the pair distribution function (PDF) analysis of intermolecular hydrogen bonds, what error bars would normally be acceptable for a good quality analysis? Maria Diaz Lopez answered: In the paper the uncertainties in the atomic positions were ca

Isoreticulation of MOFs made of pyrazole carboxylate linkers and Mn nodes is nontrivial due to linker flexibility and a variety of accessible Mn nodes. The use of tetratopic hinged linkers to form porous 3D MOFs was identified as a viable strategy.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Processible centimetre-scale porous glasses using zeolitic imidazolate framework (ZIF) materials are developed, while fine-tuning of the processing conditions allows control of pore size and molecular sieving properties.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Mn(diimine)(CO)(3)X (X = halide) complexes are critical components of chromophores, photo- and electrocatalysts, and photoactive CO-releasing molecules (photoCORMs). While these entities have been incorporated into metal-organic frameworks (MOFs), a detailed understanding of the photochemical and chemical processes that occur in a permanently porous support is lacking. Here we site-isolate and study the photochemistry of a Mn(diimine)(CO)(3)Br moiety anchored within a permanently porous MOF support, allowing for not only the photo-liberation of CO from the metal but also its escape from the MOF crystals. In addition, the high crystallinity and structural flexibility of the MOF allows crystallographic snapshots of the photolysis products to be obtained. We report these photo-crystallographic studies in the presence of coordinating solvents, THF and acetonitrile, showing the changing coordination environment of the Mn species as CO loss proceeds. Using time resolved experiments, we report complementary spectroscopic studies of the photolysis chemistry and characterize the final photolysis product as a possible Mn(ii) entity. These studies inform the chemistry that occurs in MOF-based photoCORMs and where these moieties are employed as catalysts.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Eva Meeus opened discussion of the paper by Helma Wennemers: I was wondering whether you could "revert" this process? More specifically, can you equip your peptide-based template to enable length-controlled scissions of oligomers to facilitate, for example, monomer recycling? Helma Wennemers answered: Yes, this i