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A set of terms, definitions, and recommendations is provided for use in the classification of coordination polymers, networks, and metal–organic frameworks (MOFs). A hierarchical terminology is recommended in which the most general term is coordination polymer. Coordination networks are a subset of coordination polymers and MOFs a further subset of coordination networks. One of the criteria an MOF needs to fulfill is that it contains potential voids, but no physical measurements of porosity or other properties are demanded per se. The use of topology and topology descriptors to enhance the description of crystal structures of MOFs and 3D-coordination polymers is furthermore strongly recommended.

The structural and magnetic properties of a range of new iron(III) bis-tridentate Schiff base complexes are described with emphasis on how intermolecular structural interactions influence spin states and spin crossover (SCO) in these d5 materials. Three pairs of complexes were investigated. The first pair are the neutral, heteroleptic complexes [Fe(3-OMe-SalEen)(thsa)] 1 and [Fe(3-MeOSalEen)(3-EtOthsa)] 2, where 3-R-HSalEen = (E)-2-(((2-(ethylamino)ethyl)imino)methyl)-6-R-phenol and 3-R-H2thsa = thiosemicarbazone-3-R-salicylaldimine. They display spin transitions above room temperature. However, 2 shows incomplete and gradual change, while SCO in 1 is complete and more abrupt. Lower cooperativity in 2 is ascribed to the lack of π–π interactions, compared to 1. The second pair, cationic species [Fe(3-EtOSalEen)2]NO3 3 and [Fe(3-EtOSalEen)2]Cl 4 differ only in the counter-anion. They show partial SCO above room temperature with 3 displaying a sharp transition at 343 K. Weak hydrogen bonds from cation to Cl− probably lead to weaker cooperativity in 4. The last pair, CsH2O[Fe(3-MeO-thsa)2] 5 and Cs(H2O)2[Fe(5-NO2-thsa)2] 6, are anionic homoleptic chelates that have different substituents on the salicylaldiminate rings of thsa2−. The Cs cations bond to O atoms of water and the ligands, in unusual ways thus forming attractive 1D and 3D networks in 5 and 6, respectively, and 5 remains HS (high spin) at all temperatures while 6 remains LS (low spin). Comparisons are made to other literature examples of Cs salts of [Fe(5-R-thsa)2]− (R = H and Br).

The tetratopic ligands 1,4-bis(2-ethylbutoxy)-2,5-bis(3,2’:6’,3’’-terpyridin-4’-yl)benzene (1) and 1,4-bis(3-methylbutoxy)-2,5-bis(3,2’:6’,3’’-terpyridin-4’-yl)benzene (2) have been prepared and characterized by 1H and 13C1H NMR, IR, and absorption spectroscopies and mass spectrometry. Reactions of 1 and 2 with cobalt(II) thiocyanate under conditions of crystal growth at room temperature result in the formation of [Co(1)(NCS)2·MeOH·3CHCl3]n and [Co(2)(NCS)2·0.8MeOH·1.8CHCl3]n. Single-crystal X-ray diffraction reveals that each crystal lattice consists of a trinodal self-penetrating (62.84)(64.82)(65.8)2 net. The nodes are defined by two independent cobalt centres and the centroids of two crystallographically independent ligands which are topologically equivalent.

Spotlight on coordination polymers: ChemPlusChem is pleased to present its special issue on coordination polymers/metal–organic frameworks (MOFs), guest‐edited by Stuart Batten, Banglin Chen and Jagadese J. Vittal. This issue features MOFs through various applications as sensors and in drug delivery, gas storage, catalysis etc.

An understanding of the atomic‐scale interactions between gas sorbent materials and their molecular guests is essential for the identification of the origins of desirable function and the rational optimization of performance. However, characterizations performed on equilibrated sorbent–guest systems may not accurately represent their behavior under dynamic operating conditions. The emergence of fast (minute‐scale) neutron powder diffraction coupled with direct, real‐time quantification of gas uptake opens up new possibilities for obtaining knowledge about concentration‐dependent effects of guest loading upon function‐critical features of sorbent materials, including atomic structure, diffusion pathways, and thermal expansion of the sorbent framework. This article presents a detailed investigation of the ultramicroporous metal–organic framework [Cu3(cdm)4] as a case study to demonstrate the variety of insights into sorbent performance that can be obtained from real‐time characterizations using neutron diffraction. Carbon capture: The ultramicroporous framework [Cu3(cdm)4] serves as a model system to demonstrate how NPD data collected under equilibrium and non‐equilibrium conditions can advance the understanding of lattice responses to the adsorption of guests such as CO2 and CD4 (cdm=carbamoyldicyanomethanide).

The carbamoylcyano(nitroso)methanide (ccnm) anion has been used for the synthesis of eight new salts, two of which are liquid at room temperature. The ionic liquid containing a large phosphonium cation displays the highest thermal stability, while the imidazolium salt is the most fluid and conductive. Analysis of the crystal structures of four of the new materials, containing pyrrolidinium and small phosphonium cations, reveals notably different anion stacking behaviour depending on the nature of the cation. The solid [ccnm] salts all display good ionic conductivities, above 1 mS cm−1 for the four different pyrrolidinium species. This, and their soft appearance, is hypothesized to be a result of the presence of both the syn and anti conformational isomers of the [ccnm] anion. Finally, solid‐state NMR linewidth analysis and second moment calculations have been used to gain further insight into the disorder within one of the pyrrolidinium plastic crystals, revealing significant, quantifiable translational motion of some fraction of the material at temperatures over 0 °C. Plastic fantastic: The first use of the carbamoylcyano(nitroso)methanide anion for the synthesis of ionic liquids produces crystal structures that depend strongly on the nature of the cation. The organic ionic plastic crystals made using this anion display good solid‐state ionic conductivities, consistent with the increasing interest in this type of material as new solid‐state electrolytes.

A new family of organic ionic materials of the dicyano(nitroso)methanide anion is reported. Six of the compounds are room‐temperature ionic liquids with low viscosities, which is a physical property highly desired for many synthetic and electrochemical applications. In addition, use of dimethylpyrrolidinium and tetramethylammonium cations yield the first reported dicyano(nitroso)methanide organic ionic plastic crystals, which have an advantageously wide plastic phase region. The salts also exhibit good conductivities and thermal stabilities thus making them suitable as liquid or solid‐state electrolytes for a range of electrochemical devices. Plastic crystals: The dicyano(nitroso)methanide anion has been used to produce a new series of ionic liquids with low viscosities and good ionic conductivities, in addition to new organic ionic plastic crystals with desirable phase behaviour (see structure; O red, N blue; C green).

A series of soluble metal ethylxanthate compounds was synthesised as precursors for metal sulfide thin films to be deposited using solution‐based techniques. Initially, a range of air‐ and moisture‐stable organic ethylxanthate (EtXn) salts were synthesised (cation=Me4N (1), Et4N (2), Pr4N (3), Ph4P (4), guanidinium (5), NMeH3 (6), NMe2H2 (7), NMe3H (8), NH4 (9)). Thermogravimetric analysis (TGA) was used to examine their decomposition profiles, which in turn informed the decision of which counter cation was best suited for inclusion in the metal xanthate compounds. Periodic NMR spectroscopy studies and single‐crystal X‐ray diffraction (SXRD) were used to determine the role protic ammonium counter cations play in the detrimental conversion of xanthates to dithiocarbamate anions. The organic salts 1 and 4 were used to form the metal ethylxanthate compounds (Me4N)[M(EtXn)x] (x=3 for M=Cd (10 Cd), Ni (10 Ni), Zn (10 Zn); x=4 for M=La (11 La)) and (Ph4P)[M(EtXn)3] (M=Cd (12 Cd), Ni (12 Ni), Zn (12 Zn)). Solubility studies on these compounds were performed using a range of solvents to demonstrate the viability of using these compounds for solution‐based deposition methods for thin‐film formation. TGA of the metal xanthate compounds was used to examine their thermal‐decomposition profiles and the product resulting from thermolysis was found to be the respective metal sulfide. In addition, the coproducts of thermal decomposition were analysed by headspace gas‐chromatography mass spectrometry (HS GC–MS) to probe the decomposition mechanism of the precursors. In situ variable‐temperature synchrotron XRD studies on both bulk and thin‐film samples of 10 Cd and 12 Cd were used to examine metal sulfide crystalline phase formation. Decomposition of both precursors was found to give CdS in a hexagonal phase, with the addition of CdCl2 found to aid in increasing the crystallite size during crystallisation. Film studies: A range of metal ethylxanthate compounds that are highly soluble in benign solvents have been demonstrated to thermolyse cleanly to give metal sulfide thin films (see figure). The evolution of the crystalline metal sulfide thin films deposited by solution‐processable methods were examined by using synchrotron‐based in situ variable‐temperature X‐ray diffraction measurements.

Luminescent metal–organic frameworks (LMOFs) containing fluorescent probes for the detection of pollutants such as organic solvents and heavy metals are becoming increasingly important, with lanthanide‐MOF (Ln‐MOF) materials receiving greater attention owing to the possibility of achieving fine‐tuned luminescent properties. Herein, two unusual isostructural nanocage‐based three‐dimensional Ln‐MOFs, 1 ‐Ln (Ln=Tb, Eu), are constructed, using a new diisophthalate ligand with active Lewis basic triazole sites. Selective gas adsorption, especially the removal of CO 2 from CH 4 , a primary component of natural gas and biogas, is desirable in terms of both economic and environmental considerations. 1 ‐Eu is found to exhibit highly efficient luminescent sensing for Fe 3+ cations and Cr 2 O 7 2− anions, as well as selective CO 2 capture over CH 4 .