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Covalent organic frameworks (COFs), an emerging class of crystalline polymers, are meticulously constructed through covalent bonds, resulting in well‐defined structures and crystalline characteristics. Precise control over their architecture, permeability, and functionality can be easily achieved simply via selection of precursor monomers. The tailored architecture and functionality make COFs versatile for various applications including gas storage, pollutant removal, catalysis, and energy storage. Efficient synthesis of COFs with high crystallinity and high yield significantly improves their performance. However, conventional synthetic methods often involve complex setups and costs. Innovations in catalysis have emerged as solutions, including refined activation procedures, novel catalysts, and alternative synthesis conditions. This review comprehensively explores current catalysis systems for COF synthesis, detailing catalysts for various linkages, elucidating mechanisms, and addressing challenges. Future directions and extensions of COF synthesis and applications are also highlighted. [ABSTRACT FROM AUTHOR]

Crystal and electronic structures of a newly synthesized thiazolium pentaiodide, C3H4NS(I5), were examined in detail. The title pentaiodide crystallizes in the monoclinic space group P21/m with the unit cell volume of 1289.27(6) Å3. Its crystal structure features branched pentaiodide chains composed of alternating I3− and I2 building units, whereas the chains are further linked into a 3D array by thiazolium cations with the help of (N)H⋅⋅⋅I and S⋅⋅⋅I bonds. The electronic structure and bonding assessed by DFT calculations show that covalent interactions within the I2 and I3− units are supplemented by non-covalent (N)H⋅⋅⋅I and S⋅⋅⋅I interactions, which were revealed by the electron localization function and reduced density gradient analyses. [ABSTRACT FROM AUTHOR]

Tin selenide (SnSe) is a layered semiconductor, which is reported to be the best thermoelectric material to date. Few-layer tin selenide is highly sensitive to external conditions such as strain, pressure, or temperature. Crystal structure of SnSe is orthorhombic, where atoms are arranged in an accordionlike structure with nonbonding intralayer interactions. Bulk and few-layer pristine SnSe are reported to have indirect electron bandgaps. Based on the results from first-principles density functional theory calculations, we show that two major structural changes can happen upon substitutional chemical doping of bilayer SnSe. Substitutional chemical doping can manipulate the directionality of interlayer interactions of bilayer SnSe, which results in an indirect-direct transition of the electronic bandgap. Our results also suggest that larger dopant atoms can convert the nonbonding intralayer interactions to covalent bonding. Such an increase in the atomic orbital overlap may result in a semiconductor-semimetal transition. [ABSTRACT FROM AUTHOR]

Application of chemical bonding analysis in position-space techniques based on combined topological analysis of the electron density and electron-localizability indicator distributions has recently led to the formulation of a polarity-extended 8 − Neff rule for consistent inclusion of quantum chemically obtained polar-covalent bonding data into the classical 8 − N scheme for main-group compounds. Previous application of this scheme to semiconducting main-group compounds of the cubic MgAgAs type of structure with 8 valence electrons per formula unit (8 ve per f.u.) has shown a covalent bonding tendency preferring one zinc blende type partial structure over the other one, which seems to corroborate the classical Lewis picture of maximally four covalent bonds per main-group element. In contrast to the MgAgAs type, the orthorhombic TiNiSi type of structure displays a much higher geometrical flexibility to incorporate different kinds of metal atoms. The analysis of polar-covalent bonding in semiconducting 8 ve per f.u. containing main-group compounds AA′E of this structure type reveals a transition to non-Lewis type bonding scenarios of species E with up to ten polar-covalently bonded metal atoms. This kind of situation is consistently included into the extended 8 − Neff type bonding scheme. A systematic increase of partially covalent bonding from chalcogenides E16 to the tetrelides E14 is found, summing up to as much as 2 covalent bonds E14–A and E14–A′, and correspondingly remaining 4 lone pair type electrons on species E14. The familiar notion of this structure type consisting of a '[NiSi]'-type framework with 'Ti'-type atoms filling the voids cannot be supported for the compounds investigated. [ABSTRACT FROM AUTHOR]

The title SnIV complex, [Sn(C6H5)3Cl(C18H15O4P)], is a formal adduct between triphenyl phosphate (PhO)3P O and the stannane derivative chloridotriphenyltin, SnPh3Cl. The structure refinement reveals that this molecule displays the largest Sn--O bond length for compounds including the X=O→SnPh3Cl fragment (X = P, S, C, or V), 2.6644 (17) Å. However, an AIM topology analysis based on the wavefunction calculated from the refined X-ray structure shows the presence of a bond critical point (3,-1), lying on the interbasin surface separating the coordinated phosphate O atom and the Sn atom. This study thus shows that an actual polar covalent bond is formed between (PhO)3P=O and SnPh3Cl moieties. [ABSTRACT FROM AUTHOR]

Health problems associated with excess calories, such as diabetes and obesity, have become serious public issues worldwide. Innovative methods are needed to reduce food caloric impact without negatively affecting sensory properties. The interaction between starch and phenolic compounds has presented a positive impact on health and has been applied to various aspects of food. In particular, an interaction between polyphenols and starch is widely found in food systems and may endow foods with several unique properties and functional effects. This review summarizes knowledge of the interaction between polyphenols and starch accumulated over the past decade. It discusses changes in the physicochemical properties, in vitro digestibility, prebiotic properties, and antioxidant activity of the starch–polyphenol complex. It also reviews innovative methods of obtaining the complexes and their applications in the food industry. For a brief description, phenolic compounds interact with starch through covalent or non-covalent bonds. The smoothness of starch granules disappears after complexation, while the crystalline structure either remains unchanged or forms a new structure and/or V-type complex. Polyphenols influence starch swelling power, solubility, pasting, and thermal properties; however, research remains limited regarding their effects on oil absorption and freeze–thaw stability. The interaction between starch and polyphenolic compounds could promote health and nutritional value by reducing starch digestion rate and enhancing bioavailability; as such, this review might provide a theoretical basis for the development of novel functional foods for the prevention and control of hyperglycemia. Further establishing a comprehensive understanding of starch–polyphenol complexes could improve their application in the food industry. [ABSTRACT FROM AUTHOR]

The recent synthesis of single‐layer Janus‐type transition metal dichalcogenides (TMDs) raises the question of the existence of other possible 2D structures with an asymmetric out‐of‐plane structural configuration. In the present work, a theoretical search for new Janus structures having SMoSe and SVSe compositions is performed. A detailed crystal‐chemical analysis of the predicted structures is carried out, and it is shown that some of the dynamically stable structures are characterized by crystal‐chemical features that are unique among TMDs, including quadruple Mo—Mo bonds and covalent S—S and Se—Se bonds. It is also shown that Mo‐bearing TMDs have a tendency to form strong Mo—Mo bonds with chains or isolated dimers of molybdenum atoms, while in the case of vanadium‐containing TMDs this feature is not characteristic. Two predicted crystal structures, called 1M‐SVSe and 1A′‐SMoSe, are especially promising for experimental synthesis and practical applications owing to their dynamical stability and rather low value of enthalpy compared with known structures. The enthalpy of 1M‐SVSe is 0.22 eV per formula unit lower than that of 1T‐SVSe, while the enthalpy of 1A′‐SMoSe is 0.12 eV per formula unit lower than the enthalpy of 1T‐SMoSe. The performed topological analysis showed that the predicted structures are unique and do not have analogues in the Inorganic Crystal Structure Database. [ABSTRACT FROM AUTHOR]

3‐Hydroxypiperidinium pentaiodide was synthesized by a facile reaction in concentrated aqueous HI. Its crystal structure comprises 3‐hydroxypiperidinium cations and pentaiodide anions, the latter having geometry of cis‐shaped chains composed of I2 and I3− building units. The analysis of interatomic distances, Raman spectroscopy data, and results of DFT calculations, including non‐covalent interaction analysis, showed that the title compound exhibits a complex pattern of covalent and non‐covalent interactions. Those include I−I covalent bonds and I⋅⋅⋅I halogen bonds within the I5− anion as well as (N)H⋅⋅⋅I and (O)H⋅⋅⋅I hydrogen bonds and even weaker (C)H⋅⋅⋅I van‐der‐Waals interactions between the cations and anions. [ABSTRACT FROM AUTHOR]

3‐Hydroxypiperidinium pentaiodide was synthesized by a facile reaction in concentrated aqueous HI. Its crystal structure comprises 3‐hydroxypiperidinium cations and pentaiodide anions, the latter having geometry of cis‐shaped chains composed of I2 and I3− building units. The analysis of interatomic distances, Raman spectroscopy data, and results of DFT calculations, including non‐covalent interaction analysis, showed that the title compound exhibits a complex pattern of covalent and non‐covalent interactions. Those include I−I covalent bonds and I⋅⋅⋅I halogen bonds within the I5− anion as well as (N)H⋅⋅⋅I and (O)H⋅⋅⋅I hydrogen bonds and even weaker (C)H⋅⋅⋅I van‐der‐Waals interactions between the cations and anions. [ABSTRACT FROM AUTHOR]

Supramolecular stabilization of polyiodides and iodine-dense phases is of high interest: this study explores the possibilities offered in this sense by diprotonated cyclen, affording two novel crystal structures. One of them contains at least one peculiar I⋯I interatomic distance (3.305(1) Å), falling well below the region commonly described by secondary bonding (3.4–3.7 Å) and essentially equal to the accepted limit for covalent bonding (3.30 Å): in other words, according to threshold distance values, we are relatively free to regard this interaction either as a bond or as contact. Lest the flip of a coin decides if we should or should not draw a bond in a polyiodide, statistical insights based on CSD surveys were used to put in perspective literature material and work out a meaningful assignment (as I82−). In doing so, we address how currently accepted threshold distance values came to be in the first place, their significance, soundness, and shortcomings in describing I82− and its formal fragments (I2, I3−, I5−). Discussion of the chemical meaning of the line representing bonding in I–I fragments in similar fringe cases, relating CSD data herein presented with the previous literature, is provided. Available information coincides quite well in supporting the necessity of a revision of broadly accepted threshold distance values. [ABSTRACT FROM AUTHOR]

We report the first examples of metal‐promoted double geminal activation of C(sp3)−H bonds of the N−CH2−N moiety in an imidazole‐type heterocycle, leading to nickel and palladium N‐heterocyclic carbene complexes under mild conditions. Reaction of the new electron‐rich diphosphine 1,3‐bis((di‐tert‐butylphosphaneyl)methyl)‐2,3‐dihydro‐1H‐benzo[d]imidazole (1) with [PdCl2(cod)] occurred in a stepwise fashion, first by single C−H bond activation yielding the alkyl pincer complex [PdCl(PCsp3HP)] (3) with two trans phosphane donors and a covalent Pd−Csp3 bond. Activation of the C−H bond of the resulting α‐methine Csp3 H−M group occurred subsequently when 3 was treated with HCl to yield the NHC pincer complex [PdCl(PCNHCP)]Cl (2). Treatment of 1 with [NiBr2(dme)] also afforded a NHC pincer complex, [NiBr(PCNHCP)]Br (6), but the reactions leading to the double geminal C−H bond activation of the N−CH2−N group were too fast to allow identification or isolation of an intermediate analogous to 3. The determination of six crystal structures, the isolation of reaction intermediates and DFT calculations provided the basis for suggesting the mechanism of the stepwise transformation of a N−CH2−N moiety in the N−CNHC−N unit of NHC pincer complexes and explain the key differences observed between the Pd and Ni chemistries. [ABSTRACT FROM AUTHOR]

Keywords: Gungerite; new mineral species; Tl-As-Sb sulfosalt; Raman spectroscopy; crystal structure; covalent bonds; Vorontsovskoe gold deposit EN Gungerite new mineral species Tl-As-Sb sulfosalt Raman spectroscopy crystal structure covalent bonds Vorontsovskoe gold deposit 1164 1173 10 06/01/22 20220601 NES 220601 Introduction Thallium and its compounds play a very important role in a wide variety of industrial applications ([9]; https://www.usgs.gov/centers/nmic/thallium-statistics-and-information): they are applied in the manufacture of electronic devices, optical lenses with a high-refractive index, semiconductor materials, alloys, radiation detection equipment, infrared radiation detection and transmission equipment, crystalline filters for light diffraction for acoustic-optical measuring devices, low-temperature thermometers, in the synthesis of organic compounds, and in a high-density liquid for sink-float separation of minerals. [Extracted from the article]

In this study, TiN films doped with different copper contents (TiCuN) were prepared by using direct current magnetron sputtering method. The effects of Cu doping on composition, structure, and mechanical properties of TiN films were studied by energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), a Vickers microhardnessmeter, and density functional theory (DFT). The results of experimental and DFT study showed that Cu mainly replaced Ti atoms in TiN to form replacement solid solution doping. When Cu replaced Ti in TiN, a weak Cu-N (bond population varied from 0.06 to 0.11) covalent bond formed; meanwhile, the bonding strength of Ti-N (bond population varied from 0.29 to 0.4) bond adjacent to Cu increased. When Cu content was low, a small number of weak Cu-N bonds were formed, with strengthened Ti-N bond near Cu atom, resulting in an increased hardness of Cu doped TiN films. According to the theory of weak bonds, when the Cu content was increased further, the number of weak Cu-N bonds increased and TiCuN hardness decreased. With an increase in Cu content, it was found the toughness of TiCuN also increased. The results of this study will provide a theoretical and experimental guidance for improving the toughness and deformation resistance of TiN, which has a potential application in the surface modification of medical devices. [ABSTRACT FROM AUTHOR]

Mitogen-activated protein kinases (MAPKs), including extracellular signal-regulated kinase 2 (ERK2) and p38α MAP kinase (p38α MAPK), regulate various cellular responses. ERK2 is a drug target for treating many diseases, such as cancer, whereas p38α has attracted much attention as a promising drug target for treating inflammatory disorders. ERK2 is a critical off-target for p38α MAPK and vice versa. In this study, an allosteric ERK2 inhibitor with a benzothiazole moiety (compound 1) displayed comparable inhibitory activity against p38α MAPK. Crystal structures of these MAPKs showed that compound 1 bound to the allosteric site of ERK2 and p38α MAPK in distinct manners. Compound 1 formed a covalent bond with Cys162 of p38α MAPK, whereas this covalent bond was absent in the ERK2 complex even though the corresponding cysteine is conserved in ERK2. Structural dissection combined with computational simulations indicated that an amino acid difference in the allosteric site is responsible for the distinct binding modes of compound 1 with ERK2 and p38α MAPK. These structural insights underline the feasibility of developing highly selective and potent ERK2 and p38α MAPK inhibitors. • Crystal structures of ERK2 and p38α MAPK complexed with an inhibitor were determined. • The structures showed that the inhibitor binds to these kinases in distinct manners. • Structural dissection and MD simulations elucidated the determinants for the distinct modes. • These advance the development of potent and selective inhibitors for both kinases. [ABSTRACT FROM AUTHOR]

The unique electronic structure and crystal structure driven by external pressure in transition metal tellurides (TMTs) can host unconventional quantum states. Here, the discovery of pressure‐induced phase transition at ≈2 GPa, and dome‐shaped superconducting phase emerged in van der Waals layered NbIrTe4 is reported. The highest critical temperature (Tc) is ≈5.8 K at pressure of ≈16 GPa, where the interlayered Te–Te covalent bonds form simultaneously derived from the synchrotron diffraction data, indicating the hosting structure of superconducting evolved from low‐pressure two‐dimensional (2D) phase to three‐dimensional (3D) structure with pressure higher than 30 GPa. Strikingly, the authors have found an anisotropic transport in the vicinity of the superconducting state, suggesting the emergence of a "stripe"‐like phase. The dome‐shaped superconducting phase and anisotropic transport are possibly due to the spatial modulation of interlayer Josephson coupling. [ABSTRACT FROM AUTHOR]

Using the evolutionary methodology for crystal structure prediction, we have predicted the orthorhombic Cmcm and Pnma phases for ScB4. The earlier proposed CrB4-, FeB4-, MnB4-, and ReP4-type structures for ScB4 are excluded. It is first discovered that the Cmcm phase transforms to the Pnma phase at about 18 GPa. Moreover, both phases are dynamically and mechanically stable. The large bulk modulus, shear modulus, and Young's modulus of the two phases make it an optimistic low compressible material. Moreover, the strong covalent bonding nature of ScB4 is confirmed by the ELF analysis. The strong covalent bonding contributes greatly to its stability. [ABSTRACT FROM AUTHOR]

A beam of electrosprayed nanodroplets impacting on single-crystal silicon amorphizes a thin surface layer of a thickness comparable to the diameter of the drops. The phase transition occurs at projectile velocities exceeding a threshold, and is caused by the quenching of material melted by the impacts. This article demonstrates that the amorphization of silicon is a general phenomenon, as nanodroplets impacting at sufficient velocity also amorphize other covalently bonded crystals. In particular, we bombard single-crystal wafers of Si, Ge, GaAs, GaP, InAs, and SiC in a range of projectile velocities, and characterize the samples via electron backscatter diffraction and transmission electron microscopy to determine the aggregation state under the surface. InAs requires the lowest projectile velocity to develop an amorphous layer, followed by Ge, Si, GaAs, and GaP. SiC is the only semiconductor that remains fully crystalline, likely due to the relatively low velocities of the beamlets used in this study. The resiliency of each crystal to amorphization correlates well with the specific energy needed to melt it except for Ge, which requires projectile velocities higher than expected. [ABSTRACT FROM AUTHOR]

G protein-coupled receptor kinase 5 (GRK5) is an important drug development target for heart failure, cardiac hypertrophy, and cancer. We have designed and developed a new class of highly selective, potent, and non-covalent GRK5 inhibitors. One of the inhibitors displayed GRK5 IC 50 value of 10 nM and exhibited >100,000-fold selectivity over GRK2. The X-ray structure of a ketoamide-derived inhibitor-bound GRK5 showed the formation of a hemithioketal intermediate with active site Cys474 in the GRK5 active site and provided new insights into the ligand-binding site interactions responsible for high selectivity. The current studies serve as an important guide to therapeutic GRK5 inhibitor drug development. [Display omitted] • Design and synthesis of potent and selective GRK5 inhibitors are reported. • Inhibitors form a reversible covalent bond with Cys474 in the active site. • Syntheses of GRK5 inhibitors were achieved in an efficient manner. • Two X-ray crystal structures of inhibitor bound GRK5 were determined. • The X-ray structure shows the formation of a covalent bond with catalytic Cys474. [ABSTRACT FROM AUTHOR]

Phase‐change material (PCMs) store data using the contrast (electrical or optical) between two phases: a conductive crystalline phase and a weakly conductive amorphous phase. Most PCMs have a distorted octahedral structure. The contrast comes mainly from the electronic structure. In PCMs, a spontaneous symmetry breaking mechanism, the Peierls distortion, transforms the metallic crystalline structure into a lower‐density semiconducting structure. In a simple tight‐binding model of the covalent bond, the parameters that control this distortion, characterized by a parameter η, are analyzed. The effective interatomic potential E(η) is developed in a Landau‐type series in η: E(η) = E0 + E2η2 + E4η4. The PCMs with the largest contrast are those for which the effective potential E(η) of the crystalline phase has a disappearing harmonic contribution (E2=0) and a vanishing electronic gap. This is called as an "incipient Peierls distortion." It coincides with the so‐called "incipient metal". The hardness of the repulsive potential and the number of electrons per atom play an important role. The vibrational properties and the anomalous Grüneisen parameter, specific to PCMs, are also studied. [ABSTRACT FROM AUTHOR]

Compounds containing the dioxychloronium cation, [ClO2]+, were obtained from reactions of ClF3 with various oxides such as TiO2, MoO3, Re2O7, SnO, P2O5, As2O5, and Nb metal, as the latter contained oxide as an impurity. Partial hydrolysis of [ClF2][IrF6] led to the formation of [ClO2][IrF6]. The crystal structures of the compounds were determined by single‐crystal X‐ray diffraction, which showed that depending on the starting material [ClO2]+ salts with the fluoridometallate anions [TiF3/2F3/1]2]−, [Nb3F16]−, [IrF6]−, [SnF2/2F4/1]− [PF6]−, and [AsF6]−, or with the oxidofluoridometallate anions [Mo3O3F13]− and [Re3O6F10]−, were obtained. Bent [ClO2]+ cations with short Cl ⋅ ⋅ ⋅ μ−F contacts of surrounding F atoms of the anions with the Cl atom are present in the crystal structures, leading to coordination numbers of 2+4 or 2+6 for the Cl atom. Various structural motifs are observed, which range from molecular, columnar, ladder‐like, to layer and framework structures. The salts were furthermore characterized by Raman spectroscopy and solid‐state quantum‐chemical calculations. Covalent Cl−O bonds and ionic Cl ⋅ ⋅ ⋅ μ−F interactions are indicated by the calculations. [ABSTRACT FROM AUTHOR]

Several decades ago, Mo2B was assumed to have an Al2Cu-type structure with I4/mcm space group. Using ab initio phonon calculations, we identify the earlier proposed Al2Cu-type structure is dynamically unstable at ambient pressure. An energetically more favorable phase with the tetragonal I4/m structure was then predicted by employing frozen-phonon technique. The currently predicted I4/m phase is mechanically and dynamically stable and energetically more favorable than that of the earlier proposed Al2Cu-type structure. The electronic structures calculations indicate that Mo2B is a metal with several bands crossing the Fermi level. Our analysis indicates that the three-dimensional network of the covalent Mo-B bond is responsible for the ultra-incompressible property of Mo2B. [ABSTRACT FROM AUTHOR]

A novel polyoxomolybdate with a diprotonated porphyrin as counter‐cation, namely, 5,10,15,20‐tetrakis(4‐carboxyphenyl)‐21H,22H,23H,24H‐porphine(2+) hexamolybdate(VI) pentahydrate, (C48H32N4O8)[Mo6O19]·5H2O or (H2TCPP)[Mo6O19]·5H2O, I, was prepared via the hydrothermal reaction of MoCl5, 5,10,15,20‐tetrakis(4‐carboxyphenyl)‐21H,23H‐porphine (TCPP) and distilled water. The crystal structure of hydrated polyoxometalate (POM) salt I was characterized by single‐crystal X‐ray diffraction. The compound is characterized by an isolated (zero‐dimensional, 0D) structure, because it cannot extend via covalent bonds. The structure contains one [Mo6O19]2− anion, one (H2TCPP)2+ cation and five lattice water molecules. Each of the Mo6+ ions is six‐coordinated and displays a distorted octahedral motif. The (H2TCPP)2+ cation displays a distorted saddle motif. A three‐dimensional (3D) supramolecular framework is formed via hydrogen‐bonding interactions. The compound shows a red photoluminescence emission. [ABSTRACT FROM AUTHOR]

Crystal structures of two uranyl selenite minerals derriksite, Cu4[(UO2)(SeO3)2](OH)6, and demesmaekerite, Pb2Cu5[(UO2)2(SeO3)6(OH)6](H2O)2, which structures are based on uranyl selenite 1D structural units, were studied employing single-crystal X-ray diffraction analysis at various temperatures. The refinement of their crystal structures reveals the detailed dynamics of the interatomic interactions during the heating process, which allows describing the thermal behavior. Uranyl selenite chains and their mutual arrangement mainly provide the rigidity of the crystal structure. Thus the lowest expansion in the structure of derriksite is observed along the direction of uranyl selenite chains, while the largest expansion occurs in the direction normal to chains, with the space occupied by lone electron pairs of Se4+ atoms and low covalent bond distribution density. The maximal expansion in the crystal structure of demesmaekerite is manifested approximately along the [100], which matches the direction of chains of less strongly bonded Cu-centered octahedra, and gaps between Cu chains occupied by the Pb cations. The crystal structure of demesmaekerite undergoes contraction in the direction of the space between the U-bearing chains with the deficiency of strong covalent bonds. Contraction of the structure can also be attributed to the orthogonalization of the oblique triclinic angles of the unit cell. It is demonstrated that the assignment of U-bearing units during structure description is reasonably justified since, regardless of their dimensionality, these substructural units are one of the most stable and rigid blocks in the structural architecture, and they govern the thermal behavior of the entire structure. [ABSTRACT FROM AUTHOR]

The structures of tolfenamic acid [TFA; 2-(3-chloro-2-methyl­anilino)benzoic acid, C14H12ClNO2] polymorph forms I and II have been redetermined [compare Andersen et al. (1989). J. Chem. Soc., Perkin Trans. 2, pp. 1443–1447] with improved precision using high-resolution X-ray diffraction data and Hirshfield atom refinement in order to better define both hydrogen-atom locations and their associated bond lengths. Covalent bond lengths to hydrogen were found to be significantly longer throughout both structures, especially for the anilino H atom, which is involved in an important intra­molecular N—H...O hydrogen bond to the carb­oxy­lic acid group. This hydrogen bond is shown to clearly perturb the electron density around both oxygen atoms in the latter group. The extended structures of both polymorphs feature carb­oxy­lic acid inversion dimers. These structures provide an improved foundation for nuclear magnetic resonance studies in both solution and the solid state. [ABSTRACT FROM AUTHOR]

Water can form a vast number of topological frameworks owing to its hydrogen-bonding ability, with 19 different forms of ice experimentally confirmed at present. Here, the authors comment on open questions and possible future discoveries, covering negative to ultrahigh pressures. [ABSTRACT FROM AUTHOR]

Applying Schlippe's salt, Na3SbS4·9H2O, in the presence of the in‐situ formed [Mn(terpy)]2+ complex (terpy = 2,2':6',2''‐terpyridine) the new compound {[(Mn(terpy))2Sb4S8]·0.5H2O}n (I) could be obtained under solvothermal conditions. Interestingly, in the crystal structure the two unique Mn2+ cations adopt different environments to form a MnN3S3 octahedron and a MnN3S2 trigonal pyramid. The trigonal pyramidal SbS33– anions share common edges yielding a Sb8S8 ring. Covalent bonds between Mn2+ and S2– generate MnSb2S3 and Mn2Sb4S6 heterocycles. The Sb8S8 and Mn2Sb4S6 rings are condensed to form a chain. The MnN3S3 octahedron and the MnN3S2 polyhedron share a common S2– anion and antiferromagnetic properties are observed mediated by superexchange interactions. {[(Mn(terpy))2Sb4S8]·0.5H2O}n shows luminescence in the blue‐green spectral range, assigned to combined contributions from Mn2+ ions and from the organic ligand. [ABSTRACT FROM AUTHOR]

Applying Schlippe's salt, Na3SbS4·9H2O, in the presence of the in‐situ formed [Mn(terpy)]2+ complex (terpy = 2,2':6',2''‐terpyridine) the new compound {[(Mn(terpy))2Sb4S8]·0.5H2O}n (I) could be obtained under solvothermal conditions. Interestingly, in the crystal structure the two unique Mn2+ cations adopt different environments to form a MnN3S3 octahedron and a MnN3S2 trigonal pyramid. The trigonal pyramidal SbS33– anions share common edges yielding a Sb8S8 ring. Covalent bonds between Mn2+ and S2– generate MnSb2S3 and Mn2Sb4S6 heterocycles. The Sb8S8 and Mn2Sb4S6 rings are condensed to form a chain. The MnN3S3 octahedron and the MnN3S2 polyhedron share a common S2– anion and antiferromagnetic properties are observed mediated by superexchange interactions. {[(Mn(terpy))2Sb4S8]·0.5H2O}n shows luminescence in the blue‐green spectral range, assigned to combined contributions from Mn2+ ions and from the organic ligand. [ABSTRACT FROM AUTHOR]

The crystal structure of MgCoGa2 (magnesium cobalt digallide) was solved by direct methods and refined in two space groups as P21/c (standard choice) and P21/n (non‐standard choice). The refined lattice parameters for the standard choice are a = 5.1505 (2), b = 7.2571 (2), c = 8.0264 (3) Å and β = 125.571 (3)°, and for the non‐standard choice are a = 5.1505 (2), b = 7.2571 (2), c = 6.5464 (2) Å and β = 94.217 (3)°. All parameters for MgCoGa2 refined to R1 = 0.027 and wR2 = 0.042 using 594 reflections. The crystal structure peculiarities of this compound are discussed. Particular attention has been given to relationships with other similar structures, such as YPd2Si and Fe3C. Crystallographic analysis, together with linear muffin‐tin orbital electronic structure calculations, reveals the presence of three‐dimensional polyatomic nets with partial covalent bonding between the Ga atoms. [ABSTRACT FROM AUTHOR]

The crystal structure of MgCoGa2 (magnesium cobalt digallide) was solved by direct methods and refined in two space groups as P21/c (standard choice) and P21/n (non‐standard choice). The refined lattice parameters for the standard choice are a = 5.1505 (2), b = 7.2571 (2), c = 8.0264 (3) Å and β = 125.571 (3)°, and for the non‐standard choice are a = 5.1505 (2), b = 7.2571 (2), c = 6.5464 (2) Å and β = 94.217 (3)°. All parameters for MgCoGa2 refined to R1 = 0.027 and wR2 = 0.042 using 594 reflections. The crystal structure peculiarities of this compound are discussed. Particular attention has been given to relationships with other similar structures, such as YPd2Si and Fe3C. Crystallographic analysis, together with linear muffin‐tin orbital electronic structure calculations, reveals the presence of three‐dimensional polyatomic nets with partial covalent bonding between the Ga atoms. [ABSTRACT FROM AUTHOR]

The new Y2Co3Ga9 and Gd3Ru4Al12 type representatives M2T3Al9 (M = Ca, Sr, Eu; T = Ir, Pt) and M3Rh4Al12 (M = Ca, Eu) have been synthesized from the elements by heating the respective elemental compositions in sealed tantalum tubes. The samples were analysed by powder X-ray diffraction to check their purity. By applying different temperature treatments, their phase purity and crystallinity were enhanced. The crystal structures of Ca3Rh4Al12 and Eu3Rh4Al12 (hexagonal Gd3Ru4Al12 type, P63/mmc) as well as Ca2Ir3Al9 and Ca2Pt3Al9 (orthorhombic Y2Co3Ga3 type, Cmcm) were refined from single-crystal X-ray diffraction data. All structures can be described based on distorted cube-like T@Al8 units that are connected to form strands. Additionally, an Al11 supertetrahedral building block can be identified within the structures. While the trigonal bipyramidal core of the cluster contains substantial bonding interactions in the case of the M3Rh4Al12 members, the connection via common edges in the case of the M2Ir3Al9 compounds seems to weaken these interactions. The differences in the bonding situation and the question why these different structure types are formed for the different transition metals has been targeted by quantum-chemical calculations. The calculated formation energy using three different reaction paths suggests that the stability of these phases is highly dependent on the side phases involved, even though Ca3T4Al12 phases are in general thermodynamically more favourable. According to the Bader analysis of the two polyanions, an improved covalent bonding can be observed in the [T4Al12]δ− over the [T3Al9]δ− framework. [ABSTRACT FROM AUTHOR]

Recently, it was reported that tetrapeptides cyclized via lactam bond between the amino terminus and a glutamic residue in position 4 (termed here N‐lock) can nucleate helix formation in longer peptides. We applied such strategy to derive N‐locked covalent BH3 peptides that were designed to selectively target the anti‐apoptotic protein Bfl‐1. The resulting agents were soluble in aqueous buffer and displayed a remarkable (low nanomolar) affinity for Bfl‐1 and cellular activity. The crystal structure of the complex between such N‐locked covalent peptide and Bfl‐1 provided insights on the geometry of the N‐locking strategy and of the covalent bond between the agent and Bfl‐1. [ABSTRACT FROM AUTHOR]

The new compound {[Fe(cyclam)]3Nb7O22}· ≈ 19 H2O (I) was synthesized at room temperature reacting aqueous solutions of K8{Nb6O19}·16 H2O, Fe(NO3)3·9 H2O and cyclam (1,4,8,11‐tetraazacyclotetradecane). In the crystal structure the heptaniobate {Nb7O22}9– anion is observed which is expanded by three [Fe(cyclam)]3+ complexes, thus suppressing further condensations into larger aggregates. The complexes are solely bound to the three terminal O2– anions of the NbO6 octahedron which expands the hexaniobate {Nb6O19}8– anion to form the heptaniobate cluster. The two O atoms in the FeN4O2 octahedron are in cis position leading to a severe distortion of the cyclam ligand with one of the CH2–CH2–CH2–N–CH2–CH2 fragments being rotated by about 90°. The {[Fe(cyclam)]3Nb7O22} units are arranged to form channels which host the crystal water molecules. The crystal water molecules can be removed by thermal treatment. Storing the sample on air the pristine sample is recovered. [ABSTRACT FROM AUTHOR]

The effect of temperature on the crystal structure of BaSi 2 was investigated by single crystal X-ray diffraction studies at temperatures ranging from 120 to 300 K. Upon reducing the temperature from 300 to 120 K, the unit-cell volume decreased by ∼1%, while the volume of the Si 4 tetrahedra remained unchanged. First principles calculations revealed that the Si atoms form covalent bonds with three adjacent Si atoms in the Si 4 tetrahedra. These covalent bonds are speculated to be responsible for the constant volume of Si 4 upon cooling. Image 1 • The effect of temperature on the crystal structure of BaSi 2 is investigated. • The unit-cell volume decreases by ∼9% upon cooling from 300 to 120 K. • Volume of Si 4 tetrahedra remains almost unchanged between 300 and 120 K. • Si atoms form covalent bonds with three adjacent Si atoms to form Si 4 tetrahedra. • The constant volume of Si 4 with cooling is plausibly due to its covalent bonding. [ABSTRACT FROM AUTHOR]

For further understanding of the various configurations of intermediate compounds in LiBH 4 dehydrogenation, we used a crystal structure search to propose a novel stable orthorhombic LiBH compound at ambient pressure. Imma -LiBH can be synthesized though α -LiB and H 2 and shows metallicity. The adsorption behavior investigation of H 2 on the LiBH (100) surface reveals two chemical adsorption and five physical adsorption sites. The most stable mode of H 2 adsorption occurs on the vertical hollow site. The partial density of state and electronic localization function of the mode indicate that the adsorbed H atom combine with Li and B atoms on the surface to form stable H–B covalent bond and H–Li ionic bond, respectively. Thus, Imma -LiBH can be used as a good hydrogen adsorption material for the application of electrode materials of hydrogen fuel cells. [ABSTRACT FROM AUTHOR]

An environmentally friendly procedure for the chemical modification of cellulose nanocrystals (CNCs), obtained from pine wood, was developed to manufacture hydrophobic CNCs. In comparison to other methods, this procedure has the particularity of producing a hydrophobic CNC in a single step, without using organic solvents while using MTMS as a precursor. CNCs were successfully dispersed in water, and the NMR technique was used to study the hydrolysis reaction of the MTMS in water before the surface modification of the CNCs. After 24 h of the modification reaction, the spray‐drying method was used to produce a dry powder of modified CNCs. The obtained hydrophobic CNCs were characterized by several techniques. FTIR spectroscopy confirmed the covalent bonds between the MTMS and CNCs as well as the formation of nanostructured polymethylsilsesquioxane (PMSQ) on the surface of the CNCs. XPS spectroscopy examined the presence of Si atoms of the MTMS on the surface of the CNCs. XRD detected the presence of a crystalline structure of PMSQ on the surface of the CNCs and confirmed the preservation of the CNCs crystal after the modification operation. The morphology study using SEM, AFM, and TEM techniques confirmed the presence of nanostructured PMSQ on the surfaces of modified CNCs. The hydrophobic CNCs showed a significant increase in water contact angle (110°) compared to that of unmodified CNCs (43°). This new way of modifying CNCs can produce hydrophobic CNCs with potential for dispersion in non‐polar polymers for the formulation of new nanocomposites. [ABSTRACT FROM AUTHOR]

Because cyanobacteriochrome photoreceptors need only a single compact domain for chromophore incorporation and for absorption of visible spectra including the long-wavelength far-red region, these molecules have been paid much attention for application to bioimaging and optogenetics. Most cyanobacteriochromes, however, have a drawback to incorporate phycocyanobilin that is not available in the mammalian cells. In this study, we focused on biliverdin (BV) that is a mammalian intrinsic chromophore and absorbs the far-red region and revealed that replacement of only four residues was enough for conversion from BV-rejective cyanobacteriochromes into BV-acceptable molecules. We succeeded in determining the crystal structure of one of such engineered molecules, AnPixJg2_BV4, at 1.6 Å resolution. This structure identified unusual covalent bond linkage, which resulted in deep BV insertion into the protein pocket. The four mutated residues contributed to reducing steric hindrances derived from the deeper insertion. We introduced these residues into other domains, and one of them, NpF2164g5_BV4, produced bright near-infrared fluorescence from mammalian liver in vivo. Collectively, this study provides not only molecular basis to incorporate BV by the cyanobacteriochromes but also rational strategy to open the door for application of cyanobacteriochromes to visualization and regulation of deep mammalian tissues. [ABSTRACT FROM AUTHOR]

Crystal and electronic structure of silver-containing metal-inorganic frameworks [Ag3S](NO3) and [Ag4Te](SO4) have been examined. For [Ag3S](NO3), the crystal structure has been re-determined from X-ray single crystal diffraction data and refined to R = 2.7% in order to determine the exact position of the nitrate anion. It is shown that the main structural feature of [Ag3S](NO3) and [Ag4Te](SO4) is the framework based on the combination of silver-chalcogen and silver-silver interactions, with guest oxoanions filling the cavities. Effectively, ionic interactions between guest anions and the framework differ significantly from the interactions within frameworks themselves, where the bonding analysis shows the tendency for more covalent bonding and indicates that the bonding patterns are consistent with what is regarded as metallophilic interactions. [ABSTRACT FROM AUTHOR]

Crystal and electronic structure of silver-containing metal-inorganic frameworks [Ag3S](NO3) and [Ag4Te](SO4) have been examined. For [Ag3S](NO3), the crystal structure has been re-determined from X-ray single crystal diffraction data and refined to R = 2.7% in order to determine the exact position of the nitrate anion. It is shown that the main structural feature of [Ag3S](NO3) and [Ag4Te](SO4) is the framework based on the combination of silver-chalcogen and silver-silver interactions, with guest oxoanions filling the cavities. Effectively, ionic interactions between guest anions and the framework differ significantly from the interactions within frameworks themselves, where the bonding analysis shows the tendency for more covalent bonding and indicates that the bonding patterns are consistent with what is regarded as metallophilic interactions. [ABSTRACT FROM AUTHOR]

In the course of a study on the role of magnesium in polar zincides of the heavier alkaline‐earth elements, three intermetallic phases of the ternary system Ca–Mg–Zn were synthesized from melts of the elements and their structures were determined by means of single‐crystal X‐ray data. Starting from the binary zincide CaZn11, the phase width of the BaCd11‐type structure reaches up to the fully ordered stoichiometric compound CaMgZn10 [tI48, space group I41/amd, a = 1082.66(6), c = 688.95(5) pm, Z = 4, R1 = 0.0239]. The new compound CaMgZn5 (oP28, space group Pnma, a = 867.48(3), b = 530.37(5), c = 1104.45(9) pm, Z = 4, R1 = 0.0385) crystallizes in the CeCu6‐type structure, exhibits no Mg/Zn phase width and has no binary border equivalent in the system Ca–Mg–Zn. Similar to the situation in CaMgZn10, one M position of the aristotype has a slightly larger coordination sphere (CN = 14) and is accordingly occupied by the larger Mg atoms. The third phase, Ca2+xMg6–x–yZn15+y (hP92, space group P63/mmc, a = 1476.00(5), c = 881.01(4) pm, Z = 4, R1 = 0.0399 for Ca2.67Mg5.18Zn15.15) forms the hexagonal Sm3Mg13Zn30‐type structure also known as μ‐MgZnRE or S phase. A small phase width (x = 0–0.67; y = 0–0.58) is due to the slightly variable Ca or Zn content of the two Mg positions. The structure is described as an intergrowth of the hexagonal MgZn2 Laves phase and the CaZn2 structure (KHg2‐type). All compounds exhibit strong Zn–Zn and polar Mg–Zn covalent bonds, which are visible in the calculated electron density maps. Their structures are thus herein described using the full space tilings of [Zn4] and [MgZn3] tetrahedra, which are fused to polyanions consisting of tetrahedra stars, icosahedra segments etc. and the large (CN = 18–22) Ca cation coordination polyhedra. Pseudo bandgaps apparent in the tDOS are compatible with the narrow v.e./M ranges observed for other isotypic members of the three structure types. [ABSTRACT FROM AUTHOR]

This Review presents the current status of the noble gas (Ng)‐noble metal chemistry, which began in 1977 with the detection of AuNe+ through mass spectroscopy and then grew from 2000 onwards; currently, the field is in a somewhat matured state. On one side, modern quantum chemistry is very effective in providing important insights into the structure, stability, and barrier for the decomposition of Ng compounds and, as a result, a plethora of viable Ng compounds have been predicted. On the other hand. experimental achievement also goes beyond microscopic detection and characterization through spectroscopic techniques and crystal structures at ambient temperature; for example, (AuXe4)2+(Sb2F11−)2 have also been obtained. The bonding between two noble elements of the periodic table can even reach the covalent limit. The relativistic effect makes gold a very special candidate to form a strong bond with Ng in comparison to copper and silver. Insertion compounds, which are metastable in nature, depending on their kinetic stability, display an even more fascinating bonding situation. The degree of covalency in Ng–M (M=noble metal) bonds of insertion compounds is far larger than that in non‐insertion compounds. In fact, in MNgCN (M=Cu, Ag, Au) molecules, the M−Ng and Ng−C bonds might be represented as classical 2c–2e σ bonds. Therefore, noble metals, particularly gold, provide the opportunity for experimental chemists to obtain sufficiently stable complexes with Ng at room temperature in order to characterize them by using experimental techniques and, with the intriguing bonding situation, to explore them with various computational tools from a theoretical perspective. This field is relatively young and, in the coming years, a lot of advancement is expected experimentally as well as theoretically. The test of time: The initial difficulties are in making noble‐gas compounds long after the discovery of a noble gas and, eventually, the start of noble‐gas chemistry in 1962 are described in brief. Then, the bonding between two nobles in the periodic table, that is, a noble metal and a noble gas, is summarized in chronological order. This highlights the versatile aspect of this relatively young but very promising field. The large‐scale synthesis of AuXe42+(Sb2F11−)2 is a landmark discovery in this field. [ABSTRACT FROM AUTHOR]

We present the bonding calculus, a calculus in which it is easy to handle covalent bonds between molecules. Our purpose is to use bonding calculus to model the dynamics of the interactions in biochemical systems. We provide an operational semantics by means of a transition system, and use a known software platform to both simulate the chemical reactions described naturally in bonding calculus and verify their specific properties. [ABSTRACT FROM AUTHOR]

Abstract Covalent organic frameworks (COFs) is two- or three-dimensional crystalline porous structures constructed by strong covalent bonds between organic subunits. As a new fascinating crystalline porous material, COFs have become a rapidly rising star in various fields such as gas separation and storage, catalysis, drug delivery, sensing and so on. Recently, COFs materials show great potential in analytic chemistry due to their low density, large surface areas, tunable pore size and tailored functionality. Considering that COFs have received considerable attention during the past years and will continue to be one of the interesting and hot research topics. This review describes the application of the porous COFs and their derived materials in proteomics analysis, separation and determination of various substances including harmful substances, isomers and pharmaceuticals. We also discuss the challenges and opportunities of COFs in these applications. Highlights • COFs have become a rapidly rising star in analytic chemistry. • The progress in developing COFs-based materials applied in analytic chemistry are overviewed. • The COFs and their derived materials in pretreatment, separation and determination of various samples are described. • Samples focus on proteomics, harmful substances, isomers and pharmaceuticals. [ABSTRACT FROM AUTHOR]

The phase diagram, crystal structures, electronic properties, bonding nature and superconductivities of binary Mg Bi compounds were theoretically explored under pressure. Upon compression, Mg 3 Bi, MgBi, MgBi 2 , and MgBi 3 were found to be thermodynamically stable. The stable phases present metallic features as a result of notable band structures and the finite DOS at the Fermi level. The calculated ELF and Bader charge analysis indicate that there was no covalent bond with charges transferring from Mg atoms to Bi atoms. The superconducting critical temperature ( T c ) value of Cmmm -MgBi is 8.19 K at 10 GPa. Further research reveals that bismuth phonon modes play a major role in the superconductivity of Cmmm -MgBi. This study provides the crystal structures and corresponding properties of magnesium-bismuth compounds, which has broad implications for further exploration on other bismuthides. [ABSTRACT FROM AUTHOR]

Through a structure-based irreversible drug design approach, we have discovered a highly potent IDH1-mutant inhibitor compound 16 (IHMT-IDH1-053) (IC 50 = 4.7 nM), which displays high selectivity against IDH1 mutants over IDH1 wt and IDH2 wt/mutants. The crystal structure demonstrates that 16 binds to the IDH1 R132H protein in the allosteric pocket adjacent to the NAPDH binding pocket through a covalent bond with residue Cys269. 16 inhibits 2-hydroxyglutarate (2-HG) production in IDH1 R132H mutant transfected 293T cells (IC 50 = 28 nM). In addition, it inhibits the proliferation of HT1080 cell line and primary AML cells which both bear IDH1 R132 mutants. In vivo, 16 inhibits 2-HG level in a HT1080 xenograft mouse model. Our study suggested that 16 would be a new pharmacological tool to study IDH1 mutant-related pathology and the covalent binding mode provided a novel approach for designing irreversible IDH1 inhibitors. [Display omitted] • Structure-based irreversible drug design approach leads to a novel IDH1 mutants inhibitor 16. • 16 binds to IDH1 R132H protein through a covalent bond with residue Cys269. • In vivo, 16 inhibits 2-HG level in the tumor by >85% in a HT1080 xenograft model. [ABSTRACT FROM AUTHOR]

Open-shell halogen (X = F, Cl, Br) atoms form entrance-channel complexes with H2O, which play an important role in the X + H2O reactions. To understand their structures and origin of stability, we report an extensive ab initio study of such complexes and contrast them with complexes between H2O and H/O(3P). Evidence is presented to show that the interaction between a halogen atom and H2O is dominated by a weak but covalent bond, rather than dispersion and/or electrostatic interactions. [ABSTRACT FROM AUTHOR]

In the present study, hydrogen storage reactions on Ni - C58BN and Ni - C58X2(X = B, N) heterofullerene are investigated by using the density functional theory (DFT) calculations. The Ni atom prefers to bind at the bridge site between a six-membered ring of C58BN and between a fivemembered and six-membered ring for Ni - C58X2(X = B, N), and can bind up to six hydrogen molecules with adsorption energies in the range of (-1.06, -0.31 eV) for Ni - C58BN and (-1.07, -0.33 eV) for Ni - C58B2, while (-0.86, -0.2 eV) for Ni - C58N2 per hydrogen molecule. With no metal clustering, the system gravimetric capacities are expected to be as large as 12.75, 12.77 and 12.74 wt% for 6H2 - NiC58BN, 6H2 - NiC58B2 and 6H2 - NiC58N2, respectively. While the desorption activation barriers of the complexes nH2 - NiC58BN and nH2 - NiC58B2 with n = 1 - 3 is outside the Department of Energy domain (-0.2 to -0.6 eV), and with n = 4-6 are inside this domain. For nH2 Ni - C58N2with n = 1 - 2 is outside the DOE domain, and with n = 3-6 are inside this domain. The hydrogen storage of the irreversible 3H2 + NiC58BN, 3H2 + NiC58B2, and 2H2 + NiC58N2 and reversible 4H2 + NiC58BN, 4H2 + NiC58B2 and 3H2 + NiC58N2 interactions are characterised in terms of density of states, pairwise and non-pairwise additivity, infrared, Raman (R), electrophilicity and molecular electrostatic potentials. [ABSTRACT FROM AUTHOR]

The mixed‐cation KBe2BO3F2‐type polyborate, BaLiZn3B3O9, has been obtained. It was constituted by a three‐dimensional (LiZn3B3O9)∞ network with perpendicularly connected (LiZn3B3O16)∞ layers. Within each single layer, a KBe2BO3F2‐type six‐membered ring structure is perfectly maintained. In the structure of BaLiZn3B3O9, the interlayer connection between adjacent (LiZn3B3O16)∞ layers contains not only Ba–O ionic bonds but also Zn‐O covalent bonds, which help to overcome the plate‐like growth nature of KBe2BO3F2‐type polyborates. [ABSTRACT FROM AUTHOR]

Two new bromine head-containing oxacalix[2]arene[2]triazines were designed and synthesized. Owing to the bromine head and complementary V-shaped cavity, the solid state structure of oxacalix[2]arene[2]triazine having N,N-dipropylamino substituents showed an intriguing and unique 1D-supramolecular chain-like self-assembly. To provide deep insight into the true nature of the observed stabilizing interactions, i.e., lone pair–π or σ-hole–π interactions, theoretical calculations were carried out. The computations confirm the presence of genuine σ-hole–π interactions. On the other hand, the calculations on the analogous oxacalix[2]arene[2]triazine having chlorine substituents revealed the greater π-acidic character of the s-triazine rings, thus proposing the cleft-like cavity to be more suitable for lone pair–π interactions. This is supported by retrieving the X-ray single crystal structure of the parent oxacalix[2]arene[2]triazine from the CSD which showed the existence of mixed lone pair–π/σ-hole–π and true lone pair–π interactions in the solid state. The study provides constructive clues on the utility of these macrocycles in host–guest and related fields of supramolecular chemistry. [ABSTRACT FROM AUTHOR]

Abstract: The crystal structure of [4‐damp])2[Cl4Q]3 (4‐damp=4‐dimethylamino‐N‐methylpyridinium, Cl4Q=tetrachloroquinone) salt is built up from slipped columnar stacks of quinoid rings composed of closely bound trimers with the intra‐trimer separation distance of 2.84 Å and total charge of −2 whereas the inter‐trimer distance is 3.59 Å. The individual rings exhibit partial negative charges that are distributed unevenly among the three Cl4Qs in the trimer. The strong interactions within a trimer (Cl4Q)32− have a partially covalent character with two‐electron/multicentered bonding, that is extended over three rings, plausibly termed as “pancake bonding”. The electron pairing within this multicentre bond leads to the fact that the crystals are diamagnetic and act as insulators. The studies of the structure and nature of bonding are based on X‐ray charge density analysis and density functional theory. [ABSTRACT FROM AUTHOR]

First-principles calculations were performed to investigate the bonding characteristics of the undoped and doped ZrCoH 3 and predict the anti-disproportionation abilities of alloying elements (i.e. Y, V, Nb, Ta, Zr, Cr, Mn, Ru, Rh, Pd and Zn). The binding between H and Zr (or its substitute elements) shows strong ionic and weak covalent feature, and that between H and Co (or its substitute elements) displays the opposite characteristic. The H diffusion process, the size of the 8e site and the corresponding Zr H distance were calculated, and the substitute elements of Zr (i.e. Nb, Ta and especially V) are predicted to be helpful to improve the ZrCo alloy against the hydrogen-induced disproportionation, and the substitute elements of Co may be not suitable. [ABSTRACT FROM AUTHOR]