Let’s talk about MOFs—Topology and terminology of metal-organic frameworks and why we need them

Recent IUPAC (The International Union for Pure and Applied Chemistry) recommendations on the terminology of metal-organic frameworks are reviewed and the background to a proposed topology classification is discussed. The various numerical designators such as point symbols, vertex symbols and transitivity are also explained and their importance elucidated

Network topology approach to new allotropes of the group 14 elements

The network topology approach has been a major driving force in the search for new metal-organic frameworks and coordination networks. In this work we demonstrate how this method not only generated the recently described "T12" allotrope of the group 14 elements, identical to the cdp topology found in the structure of CdP2, but also a number of other candidate structures for polymorphs of these network-forming elements. Data on such network structures have been compiled since the 1950's and is readily accessible through several internet based systems. The usefulness of topology for the classification of these allotropes is emphasised

Metal-ligand bond lengths and strengths: are they correlated? A detailed CSD analysis

Structure data on metal-alkoxides, metal-alcohol, metal-carboxylates, metal-carboxylic acid, metal-azolate and metal-azole coordination compounds from the Cambridge Structural Database (CSD) were analysed in terms of bond lengths. In general the anionic ligands form shorter metal-ligand bonds by about 0.02-0.05 angstrom compared to neutral ligands, a clear indication of a charge contribution to the bonding interactions. This small difference is not, however, deemed as sufficient to generate two distinct classes of metal-ligand bonding. Instead, the anionic ligands can be viewed as having "charge assisted" metal-ligand bonding, corresponding to the same term used for "charge-assisted hydrogen bonding"

2,3,6,7,10,11-Hexahydroxytri- phenylene tetrahydrate: a new form of an important starting material for supramolecular chemistry and covalent organic frameworks

In the title compound, C18H12O64H2O, the 2,3,6,7,10,11-hexa- hydroxytriphenylene molecule is located on a twofold axis and two water molecules occupy general positions. The compound forms (4,4) two-dimensional nets via hydrogen bonds between neighbouring hexahydroxytriphenylene molecules, somewhat similar to the cyclopentanone solvates but distinctively different from the monohydrate form. Hydrogen bonds to water molecules connect these layers to form a complicated three-dimensional net, supported also by strong %–% stacking

Teaching of chemical bonding: a study of Swedish and South African students' conceptions of bonding

Almost 700 Swedish and South African students from the upper secondary school and first-term chemistry university level responded to our survey on concepts of chemical bonding. The national secondary school curricula and most common textbooks for both countries were also surveyed and compared for their content on chemical bonding. Notable differences between the countries were found in textbooks and in the curriculum regarding the topics of ionic bonding, bond energetics and use of the VSEPR model, the latter being absent in the Swedish curriculum and ionic bonding not explicitly mentioned in the South African curriculum. To some extent these differences are reflected in the students' responses to the survey. It is also clear that university teachers in both countries must prepare effective counter-measures against deep rooted misunderstandings. For the upper secondary school level it is suggested that the bond energetics and exothermic and endothermic reactions be clearly and carefully presented and separated as the study indicates that mixing of these two concepts is a major cause of confusion

A new methanol solvate and Hirshfeld analysis of π-stacking in 2,3,6,7,10,11-hexahydroxytriphenylene solvates

The structure of 2,3,6,7,10,11-hexahydroxytriphenylene (hhtp) methanol monosolvate, C18H12O6•CH3OH, has triclinic symmetry (space group P1). The compound has a threedimensional layered network structure formed by intermolecular hydrogen bonding. Structure analysis with Hirshfeld surfaces is shown to be a sensitive method for comparing π -stacking effects in the five known solvates of hhtp. The title structure shows slightly weaker π -stacking than the dihydrate, but stronger π -stacking than the other three solvates

Four New Synthetic Elements Approved

Recently, chemists and physicists in the Joint Working Party (JWP) have approved the new elements, but what is the significance and how can we make use of elements that exist so fleetingly

The synthesis, structure, topology and catalytic application of a novel cubane-based copper(II) metal-organic framework derived from a flexible amido tripodal acid

A novel chiral metal-organic framework, [Cu-4(HL)(2)(H2O)(4)(MeO)(4)](n) (1), has been successfully synthesized from a tripodal flexible ligand (2S, 2'S, 2 '' S)- 2,2', 2 ''-(benzenetricarbonyltris(azanediyl)) tripropanoic acid (H3L). Compound 1 was characterized by IR and X-ray powder diffraction analysis. The structure was determined by X-ray single crystal diffraction analysis revealing that 1 possesses a 3D network, featuring a tetranuclear cubane-type secondary building block [Cu-4(MeO)(4)](4+), formed via the connection of four metal ions to four methoxide ions. These secondary building blocks are linked by four different HL2- ligands to construct a porous three dimensional framework of the dia topology with one-dimensional channels. Compound 1 also acts as a heterogeneous catalyst for the diastereoselective nitroaldol (Henry) reaction, providing high yields (up to 91%) and good diastereoselectivities under ambient conditions. This catalyst can be recycled without significant loss of activity

Concomitant Metal Organic Frameworks of Cobalt(II) and 3-(4-Pyridyl)benzoate: Optimized Synthetic Conditions of Solvatochromic and Thermochromic Systems

Two coordination networks, {[Co-(34pba)(2)]center dot DMF}(n) (1 and 2), where 34pba is 3-(4-pyridy1)benzoate, were prepared by solvothermal methods. 1 is a three-dimensional metal organic framework formed by linking [Co-2(34pba)(8)] clusters in a bcu net. 2 consists of single [Co(34pba)(4)] units in a tetragonal plane net of sql topology. The thermal conditions leading to their selective synthesis were established: 120 degrees C for 1 and 75 degrees C for 2. Their structures were solved and their thermal behavior was investigated. Further experiments established the activation energy for the desorption of the DMF molecules entrapped in their framework: 76(6)-106(16) kJ mol(-1) for 1 and 49(3)-58(3) kJ mol(-1) for 2. For 1, sorption experiments were carried out to demonstrate the ability of the coordination network to absorb different solvents, and the framework solvatochromic response was also ascertained

Crystal structures and hydrogen bond analysis of five amino acid conjugates of terephthalic and benzene-1,2,3-tricarboxylic acids

Four linear connecting amino acid derived ligands, 1-4, and one potentially three connecting, 5, were prepared by the reaction of the appropriate terephthaloyl dichloride or benzene-1,3,5-tricarbonyl trichloride with the methyl ester protected amino acid. Amino acids used here were alanine (1, 5), isoleucine (2), leucine (3) and valine (4). Crystalline forms of four amino acid substituted terephthalamides (2,2′-(terephthaloylbis(azanediyl)) dipropanoic acid dihydrate 1; 2,2′-(terephthaloylbis(azanediyl))bis(3- methylpentanoic acid) monohydrate 2; 2,2′-(terephthaloylbis(azanediyl)) bis(4-methylpentanoic acid) dihydrate 3; 2,2′-(terephthaloylbis(azanediyl) )bis(3-methylbutanoic acid) dihydrate 4) and one benzene-1,3,5-tricarboxamide molecule (2,2′,2′′-((benzene-1,3,5-tricarbonyl)tris(azanediyl) )tripropionic acid hemihydrate 5) were characterised and the single crystal structures were solved. All the compounds form hydrogen bonded 2D and 3D nets. Linear connecting amino acid derivatives can be categorised into three groups depending on the hydrogen bond patterns and final structures. Compounds 1 and 2 form 3D structures but the final structure is different due to the different hydrogen bond synthons. Compounds 3 and 4 are isostructural and form 2D hydrogen bonded structures while 5 forms a hydrogen bonded pcu-net. Intermolecular interactions have been analysed with Hirshfeld surfaces and graph set symbols