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Collective interactions are a novel type of chemical bond formed between metals and electron‐rich substituents around an electron‐poor central atom. So far only a limited number of candidates for having collective interactions are reported. In this work, we extend the newly introduced concept of collective bonding to a series of neutral boron complexes with the general formula M2BX3 (M=Li, Na, and K; X=F, Cl, and Br). Our state‐of‐the‐art ab initio computations suggest that these complexes form trigonal bipyramidal structures with a D3h to C3v distortion along the C3 axis of symmetry. The BX3 unit in the complexes distorts from planar to pyramidal akin to a sp3 hybridized atom. Interestingly, the interaction of the metals with the pyramidal side of BX3, where the lone pair in a hypothetical [BX3]2− should be located, is weaker than the interactions of metals with the inverted side, i. e., the middle of three halogen atoms. The origin of this stronger interaction can be explained by the formation of collective interactions between metals and halogen atoms as we explored via energy decomposition within the context of the theory of interacting quantum atoms, IQA. [ABSTRACT FROM AUTHOR]

First‐principles calculations on titania clusters (TiO2)n (n=5 and 10) supported on the pristine Ti2C (0001) surface were carried out to understand the properties of semiconductor/MXene composites with implications in (photo)‐catalysis. The reported results reveal a high exothermic interaction accompanied by a substantial charge transfer with a concomitant, notorious, deformation of the titania nanoclusters. The analysis of the density of states analysis of the composite systems evidences a metallic character with titania related states crossing the Fermi level. The picture of the chemical bonds is completed by the analysis of X‐Ray Photoelectron Spectra (XPS) features, evidencing clear shifts of the C(1s) and O(1s) related peaks relative to the isolated systems that have a quite complex origin. This detailed analysis provides insights to experimentalists interested in the design and synthesis of these systems with possible applications in catalysis. [ABSTRACT FROM AUTHOR]

Opposite to what one might expect, we find that the C=X group can become effectively more, not less, electronegative when the Pauling electronegativity of atom X decreases down Groups 16, 15, and 14 of the Periodic Table. Our quantum‐chemical analyses, show that, and why, this phenomenon is a direct consequence of the increasing size of atom X down a group. These findings can be applied to tuning and improving the hydrogen‐bond donor strength of amides H2NC(=X)R by increasingly withdrawing density from the NH2 group. A striking example is that H2NC(=SiR2)R is a stronger hydrogen‐bond donor than H2NC(=CR2)R. [ABSTRACT FROM AUTHOR]

Pyramidane molecules have attracted chemists for many decades due to their regular shape, high symmetry and their correspondence in the macroscopic world. Recently, experimental access to a number of examples has been reported, in particular the rarely reported square pyramidal bora[4]pyramidanes. To describe the bonding situation of the nonclassical structure of pyramidanes, we present solid‐state Nuclear Magnetic Resonance (NMR) as a versatile tool for deciphering such bonding properties for three now accessible bora[4]pyramidane and dibora[5]pyramidane molecules. 11B solid‐state NMR spectra indicate that the apical boron nuclei in these compounds are strongly shielded (around −50 ppm vs. BF3‐Et2O complex) and possess quadrupolar coupling constants of less than 0.9 MHz pointing to a rather high local symmetry. 13C−11B spin‐spin coupling constants have been explored as a measure of the bond covalency in the borapyramidanes. While the carbon‐boron bond to the −B(C6F5)2 substituents of the base serves as an example for a classical covalent 2‐center‐2‐electron (2c–2e) sp2‐carbon‐sp2‐boron σ‐bond with 1J(13C‐11B) coupling constants in the order of 75 Hz, those of the boron(apical)‐carbon(basal) bonds in the pyramid are too small to measure. These results suggest that these bonds have a strongly ionic character, which is also supported by quantum‐chemical calculations. [ABSTRACT FROM AUTHOR]

Intoxication is one of the most common causes of accidental death globally. Although some antidotes capable of neutralizing the toxicity of certain xenobiotics have become well established, the current reality is that clinicians primarily rely on nonspecific extracorporeal techniques to remove toxins. Nano‐intervention strategies in which nanoantidotes neutralize toxicity in situ via physical interaction, chemical bonding, or biomimetic clearance have begun to show clinical potential. However, most nanoantidotes remain in the proof‐of‐concept stage, and the difficulty of constructing clinical relevance models and the unclear pharmacokinetics of nanoantidotes hinder their translation to clinic. This Concept reviews the detoxification mechanisms of polymer nanoantidotes and predicts the opportunities and challenges associated with their clinical application. [ABSTRACT FROM AUTHOR]

Our quantum chemical analyses elucidated how the replacement of O in the amide bonds of benzene‐1,3‐5‐tricarboxamides (OBTAs) with the larger chalcogens S and Se enhances the intermolecular interactions and thereby the stability of the obtained hydrogen‐bonded supramolecular polymers due to two unexpected reasons: i) the SBTA and SeBTA monomers have a better geometry for self‐assembly and ii) induce stronger covalent (hydrogen‐bond) interactions besides enhanced dispersion interactions. In addition, it is shown that the cooperativity in benzene‐1,3,5‐triamide (BTA) self‐assembly is caused by charge separation in the σ‐electronic system following the covalency in the hydrogen bonds. [ABSTRACT FROM AUTHOR]

Melamine is a precursor and building block for graphitic carbon nitride (g‐CN) materials, a group of layered materials showing great promise for catalytic applications. The synthetic pathway to g‐CN includes a polycondensation reaction of melamine by evaporation of ammonia. Melamine molecules in the crystal organize into wave‐like planes with an interlayer distance of 3.3 Å similar to that of g‐CN. Here we present an extensive investigation of the experimental electron density of melamine obtained from modelling of synchrotron radiation X‐ray single‐crystal diffraction data measured at 25 K with special focus on the molecular geometry and intermolecular interactions. Both intra‐ and interlayer structures are dominated by hydrogen bonding and π‐interactions. Theoretical gas‐phase optimizations of the experimental molecular geometry show that bond lengths and angles for atoms in the same chemical environment (C−N bonds in the ring, amine groups) differ significantly more for the experimental geometry than for the gas‐phase‐optimized geometries, indicating that intermolecular interactions in the crystal affects the molecular geometry. In the experimental crystal geometry, one amine group has significantly more sp3‐like character than the others, hinting at a possible formation mechanism of g‐CN. Topological analysis and energy frameworks show that the nitrogen atom in this amine group participates in weak intralayer hydrogen bonding. We hypothesize that melamine condenses to g‐CN within the layers and that the unique amine group plays a key role in the condensation process. [ABSTRACT FROM AUTHOR]

One challenge in chemistry is the plethora of often disparate models for rationalizing the electronic structure of molecules. Chemical concepts abound, but their connections are often frail. This work describes a quantum‐mechanical framework that enables a combination of ideas from three approaches common for the analysis of chemical bonds: energy decomposition analysis (EDA), quantum chemical topology, and molecular orbital (MO) theory. The glue to our theory is the electron energy density, interpretable as one part electrons and one part electronegativity. We present a three‐dimensional analysis of the electron energy density and use it to redefine what constitutes an atom in a molecule. Definitions of atomic partial charge and electronegativity follow in a way that connects these concepts to the total energy of a molecule. The formation of polar bonds is predicted to cause inversion of electronegativity, and a new perspective of bonding in diborane and guanine−cytosine base‐pairing is presented. The electronegativity of atoms inside molecules is shown to be predictive of pKa. [ABSTRACT FROM AUTHOR]

After exploring the potential energy surfaces of MmCE2p (E=S−Te, M=Li−Cs, m=2, 3 and p=m‐2) and MnCE3q (E=S−Te, M=Li−Cs, n=1, 2, q=n‐2) combinations, we introduce 38 new global minima containing a planar hypercoordinate carbon atom (24 with a planar tetracoordinate carbon and 14 with a planar pentacoordinate carbon). These exotic clusters result from the decoration of V‐shaped CE22− and Y‐shaped CE32− dianions, respectively, with alkali counterions. All these 38 systems fulfill the geometrical and electronic criteria to be considered as true planar hypercoordinate carbon systems. Chemical bonding analyses indicate that carbon is covalently bonded to chalcogens and ionically connected to alkali metals. [ABSTRACT FROM AUTHOR]

In 1966, Zimmerman proposed a type of Möbius aromaticity that involves through‐space electron delocalization; it has since been widely applied to explain reactivity in pericyclic reactions, but is considered to be limited to transition‐state structures. Although the easily accessible hexahelicene radical anion has been known for more than half a century, it was overlooked that it exhibits a ground‐state minimum and robust Zimmerman‐Möbius aromaticity in its central noose‐like opening, becoming, hence, the oldest existing Möbius aromatic system and with smallest Möbius cycle known. Despite its overall aromatic stabilization energy of 13.6 kcal mol−1 (at B3LYP/6‐311+G**), the radical also features a strong, globally induced paramagnetic ring current along its outer edge. Exclusive global paramagnetic currents can also be found in other fully delocalized radical anions of 4N+2 π‐electron aromatic polycyclic benzenoid hydrocarbons (PAH), thus questioning the established magnetic criterion of antiaromaticity. As an example of a PAH with nontrivial topology, we studied a novel Möbius[16]cyclacene that has a non‐orientable surface manifold and a stable closed‐shell singlet ground state at several density functional theory levels. Its metallic monoanion radical (0.0095 eV band gap at HSE06/6‐31G* level) is also wave‐function stable and displays an unusual 4π‐periodic, magnetically induced ring current (reminiscent of the transformation behaviour of spinors under spatial rotation), thus indicating the existence of a new, Hückel‐rule‐evading type of aromaticity. [ABSTRACT FROM AUTHOR]

Although silylene‐carbonyl complexes are known for decades, only recently isolable examples have been accomplished. In this work, the bonding situation is re‐evaluated to explain the origins of their remarkable stability within the Kohn‐Sham molecular orbital theory framework. It is shown that the chemical bond can be understood as CO interaction with the silylene via a donor‐acceptor interaction: a σ‐donation from the σCO into the empty p‐orbital of silicon, and a π‐back donation from the sp2 lone pair of silicon into the π*CO antibonding orbitals. Notably, it was established that the driving force behind the surprisingly stable Si−CO compounds, however, is another π‐back donation from a perpendicular bonding R−Si σ‐orbital into the π*CO antibonding orbitals. Consequently, the pyramidalization of the central silicon atom cannot be associated with the strength of the π‐back donation, in sharp contrast to the established chemical bonding model. Considering this additional bonding interaction not only shed light on the bonding situation, but is also an indispensable key for broadening the scope of silylene‐carbonyl chemistry. [ABSTRACT FROM AUTHOR]

The clathrate I superconductor Sr8Si46 is obtained under high‐pressure high‐temperature conditions, at 5 GPa and temperatures in the range of 1273 to 1373 K. At ambient pressure, the compound decomposes upon heating at T=796(5) K into Si and SrSi2. The crystal structure of the clathrate is isotypic to that of Na8Si46. Chemical bonding analysis reveals conventional covalent bonding within the silicon network as well as additional multi‐atomic interactions between Sr and Si within the framework cages. Physical measurements indicate a bulk BCS type II superconducting state below Tc=3.8(3) K. [ABSTRACT FROM AUTHOR]

The clathrate I superconductor Sr8Si46 is obtained under high‐pressure high‐temperature conditions, at 5 GPa and temperatures in the range of 1273 to 1373 K. At ambient pressure, the compound decomposes upon heating at T=796(5) K into Si and SrSi2. The crystal structure of the clathrate is isotypic to that of Na8Si46. Chemical bonding analysis reveals conventional covalent bonding within the silicon network as well as additional multi‐atomic interactions between Sr and Si within the framework cages. Physical measurements indicate a bulk BCS type II superconducting state below Tc=3.8(3) K. [ABSTRACT FROM AUTHOR]

Valence‐shell electron‐pair repulsion (VSEPR) theory constitutes one of the pillars of theoretical predictive chemistry. It was proposed even before the advent of the concept of "spin", and it is still a very useful tool in chemistry. In this article we propose an extension of VSEPR theory to understand the core structure and predict core polarization in the main‐group elements. We show from first principles (Electron Localization Function analysis) how the inner‐ and outer‐core shells are organized. In particular, electrons in these regions are structured following the shape of the dual polyhedron of the valence shell (3rd period) or the equivalent polyhedron (4th and 5th periods). We interpret these results in terms of "hard" and "soft" core character. All the studied systems follow this trend, providing a framework for predicting electron distribution in the core. We also show that lone pairs behave as "standard ligands" in terms of core polarization. The predictive character of the model was tested by proposing the core polarization in different systems not included in the original set (such as XeF4 and [Fe(CN)6]3−) and checking the hypothesis by means of a posteriori calculations. From the experimental point of view, the extension of VSEPR to the core region has consequences for current crystallography research. In particular, it explains the core polarization revealed by high resolution X‐ray experiments. [ABSTRACT FROM AUTHOR]

The covalent nature of the low‐barrier N−H−N hydrogen bonds in the negative thermal expansion material H3[Co(CN)6] has been established by using a combination of X‐ray and neutron diffraction electron density analysis and theoretical calculations. This finding explains why negative thermal expansion can occur in a material not commonly considered to be built from rigid linkers. The pertinent hydrogen atom is located symmetrically between two nitrogen atoms in a double‐well potential with hydrogen above the barrier for proton transfer, thus forming a low‐barrier hydrogen bond. Hydrogen is covalently bonded to the two nitrogen atoms, which is the first experimentally confirmed covalent hydrogen bond in a network structure. Source function calculations established that the present N−H−N hydrogen bond follows the trends observed for negatively charge‐assisted hydrogen bonds and low‐barrier hydrogen bonds previously established for O−H−O hydrogen bonds. The bonding between the cobalt and cyanide ligands was found to be a typical donor–acceptor bond involving a high‐field ligand and a transition metal in a low‐spin configuration. [ABSTRACT FROM AUTHOR]

The covalent nature of the low‐barrier N−H−N hydrogen bonds in the negative thermal expansion material H3[Co(CN)6] has been established by using a combination of X‐ray and neutron diffraction electron density analysis and theoretical calculations. This finding explains why negative thermal expansion can occur in a material not commonly considered to be built from rigid linkers. The pertinent hydrogen atom is located symmetrically between two nitrogen atoms in a double‐well potential with hydrogen above the barrier for proton transfer, thus forming a low‐barrier hydrogen bond. Hydrogen is covalently bonded to the two nitrogen atoms, which is the first experimentally confirmed covalent hydrogen bond in a network structure. Source function calculations established that the present N−H−N hydrogen bond follows the trends observed for negatively charge‐assisted hydrogen bonds and low‐barrier hydrogen bonds previously established for O−H−O hydrogen bonds. The bonding between the cobalt and cyanide ligands was found to be a typical donor–acceptor bond involving a high‐field ligand and a transition metal in a low‐spin configuration. [ABSTRACT FROM AUTHOR]

Growing demands of material science and, in particular, in the field of nonlinear optics (NLO) encourage us to look for stable highly polarizable molecules with excess diffuse electrons. An unusual class of compounds called electrides comply with these requirements. Many attempts have been made, yet only few electrides have been synthesized as solids and none of them as molecular species. In this paper, a new theoretically designed molecular species with electride characteristics is reported. The idea of this molecular electride comes from the formation of electride‐like features in the MgO crystal with defect F‐centers. The geometry of the investigated molecule can be described as a Mg4O4 cube with one oxygen atom removed. In Mg4O3, two 3s electrons are pushed out from the inner area of the molecule forming a diffuse electride multicentered bond. Our calculations show that this electride‐like cluster possesses a noticeably large first hyperpolarizability β=5733 au. At the same time, a complete cube Mg4O4 and Mg4O32+ without electride electron pair have much smaller β: 0 au and 741 au, respectively. This fact indicates the decisive role of the electride electron pair in NLO properties. Additionally, vertical detachment energies of isomers (VDE), excitation energies ΔE, polarizabilities α, and IR spectra were calculated. These properties, including β, are supposed to be observable experimentally and can serve as indirect evidence of the stable molecular electride formation. Elusive electride: Many attempts have been made, yet only few electrides have been synthesized as solids and none of them as molecular species. A theoretically designed molecular species with electride characteristics is reported based on the idea of formation of electride‐like features in MgO crystals with defect F‐centers. [ABSTRACT FROM AUTHOR]

Abstract: Originally, the concepts of aromaticity and antiaromaticity were introduced to explain the stability and reactivity of unsaturated organic compounds. Since then, they have been extended to other species with delocalized electrons including various saturated systems, organometallic compounds, and even inorganic clusters and molecules. In this Minireview, we focus on the most recent progress of using these concepts to guide experimental synthesis and rationalize geometrical and electronic structures of a particular family of polyanions composed of Group 14 and 15 elements, namely Zintl clusters. [ABSTRACT FROM AUTHOR]

Abstract: The concept of electronic transmutation (ET) depicts the processes that by acquiring an extra electron, an element with the atomic number Z begins to have properties that were known to only belong to its neighboring element with the atomic number Z+1. Based on ET, signature compounds and chemical bonds that are composed of certain elements can now be designed and formed by other electronically transmutated elements. This Minireview summarizes the recent developments and applications of ET on both the theoretical and experimental fronts. Examples on the ET of Group 13 elements into Group 14 elements, Group 14 elements into Group 15 elements, and Group 15 elements into Group 16 elements are discussed. Compounds and chemical bonding composed of carbon, silicon, germanium, phosphorous, oxygen and sulfur now have analogues using transmutated boron, aluminum, gallium, silicon, nitrogen, and phosphorous. [ABSTRACT FROM AUTHOR]

Abstract: We report the successful isolation and structural elucidation of two bimetallic doped [Co2@Ge16]4− clusters (α and β form), which were synthesized through the reaction of [{(ArN)2CtBu}Co(η6‐toluene)] (Ar=2,6‐diisopropylphenyl) and K4Ge9 in ethylenediamine (en) solution and co‐crystallized together in [K(2,2,2‐crypt)]4[Co2@Ge16]⋅en. The α‐[Co2@Ge16]4− isomer prefers a distinct D2h 3‐connected architecture, whereas the deltahedral isomeric β‐[Co2@Ge16]4− isomer adopts a quasi‐C2h geometry and can be seen as coupling of two distorted arachno‐[Co@Ge10] units. Chemical bonding analyses indicate that the skeleton of the α isomer is mainly composed of localized bonds, whereas only multicenter bonding interactions govern the geometry of the β isomer, which was further found to exhibit a fluxional behavior. The coexistence of both isomers within one unit cell links the 3‐connected clusters with their deltahedral congeners, thus highlighting the structural and electronic flexibility of such discreet cluster systems. [ABSTRACT FROM AUTHOR]

The discovery of the ultra-high thermoelectric figure of merit of 2.6 in SnSe has drawn attention to other lead-free IV-VI orthorhombic semiconductors. GeSe has been predicted to possess thermoelectric performances comparable to SnSe. Here, a complete structural study is reported of GeSe with temperature by means of high-resolution synchrotron powder X-ray diffraction. In the orthorhombic phase, the evolution of the bond distances with temperature is shown to deviate significantly with respect to SnSe. Analysis of the chemical bonding within the Quantum Theory of Atoms in Molecules shows that GeSe is ionic with van der Waals interlayer interactions. The signature of the N shell lone pair of Ge is also evident from both the electron density Laplacian and the ELF topologies. [ABSTRACT FROM AUTHOR]

Keywords: biomimetic clearance; chemical bonding; clinical practice; physical interaction; polymer nanoantidote EN biomimetic clearance chemical bonding clinical practice physical interaction polymer nanoantidote 1 1 1 07/28/23 20230726 NES 230726 B Polymer nanoantidotes b act as shields to protect tissue from xenobiotics by neutralizing toxicity in situ with the mechanisms of physical interaction, chemical bonding, or biomimetic clearance. Biomimetic clearance, chemical bonding, clinical practice, physical interaction, polymer nanoantidote. [Extracted from the article]

The quasibinary section of the intermetallic phases MAl4 and MGa4 with M=Sr and Ba have been characterised by means of X-ray diffraction (XRD) studies and differential thermal analysis. The binary phases show complete miscibility and form solid solutions M(Al1− xGa x)4 with M=Sr and Ba. These structures crystallise in the BaAl4 structure type with four- and five-bonded Al and/or Ga atoms (denoted as Al(4b), Al(5b), Ga(4b), and Ga(5b), respectively) that form a polyanionic Al/Ga sublattice. Solid state 27Al NMR spectroscopic analysis and quantum mechanical (QM) calculations were applied to study the bonding of the Al centres and the influence of Al/Ga substitution, especially in the regimes with low degrees of substitution. M(Al1− xGa x)4 with M=Sr and Ba and 0.925≤ x≤0.975 can be described as a matrix of the binary majority compound in which a low amount of the Ga atoms has been substituted by Al atoms. In good agreement with the QM calculations, 27Al NMR investigations and single crystal XRD studies prove a preferred occupancy of Al(4b) for these substitution regimes. Furthermore, two different local Al environments were found, namely isolated Al(4b1) atoms and Al(4b2), due to the formation of Al(4b)-Al(4b) pairs besides isolated Al(4b) atoms within the polyanionic sublattice. QM calculations of the electric field gradient (EFG) using superlattice structures under periodic boundary conditions are in good agreement with the NMR spectroscopic results. [ABSTRACT FROM AUTHOR]

Two ternary borides MNi9B8 ( M=Al, Ga) were synthesized by thermal treatment of mixtures of the elements. Single-crystal X-ray diffraction data reveal AlNi9B8 and GaNi9B8 crystallizing in a new type of structure within the space group Cmcm and the lattice parameters a=7.0896(3) Å, b=8.1181(3) Å, c=10.6497(4) Å and a=7.0897(5) Å, b=8.1579(4) Å, c=10.6648(7) Å, respectively. The boron atoms build up two-dimensional layers, which consist of puckered [B16] rings with two tailing B atoms, whereas the M atoms reside in distorted vertices-condensed [Ni12] icosahedra, which form a three-dimensional framework interpenetrated by boron porphyrin-reminiscent layers. An unusual local arrangement resembling a giant metallo-porphyrin entity is formed by the [B16] rings, which, due to their large annular size of approximately 8 Å, chelate four of the twelve icosahedral Ni atoms. An analysis of the chemical bonding by means of the electron localizability approach reveals strong covalent BB interactions and weak NiNi interactions. Multi-center dative BNi interaction occurs between the Al-Ni framework and the boron layers. In agreement with the chemical bonding analysis and band structure calculations, AlNi9B8 is a Pauli-paramagnetic metal. [ABSTRACT FROM AUTHOR]

Two ternary borides MNi9B8 ( M=Al, Ga) were synthesized by thermal treatment of mixtures of the elements. Single-crystal X-ray diffraction data reveal AlNi9B8 and GaNi9B8 crystallizing in a new type of structure within the space group Cmcm and the lattice parameters a=7.0896(3) Å, b=8.1181(3) Å, c=10.6497(4) Å and a=7.0897(5) Å, b=8.1579(4) Å, c=10.6648(7) Å, respectively. The boron atoms build up two-dimensional layers, which consist of puckered [B16] rings with two tailing B atoms, whereas the M atoms reside in distorted vertices-condensed [Ni12] icosahedra, which form a three-dimensional framework interpenetrated by boron porphyrin-reminiscent layers. An unusual local arrangement resembling a giant metallo-porphyrin entity is formed by the [B16] rings, which, due to their large annular size of approximately 8 Å, chelate four of the twelve icosahedral Ni atoms. An analysis of the chemical bonding by means of the electron localizability approach reveals strong covalent BB interactions and weak NiNi interactions. Multi-center dative BNi interaction occurs between the Al-Ni framework and the boron layers. In agreement with the chemical bonding analysis and band structure calculations, AlNi9B8 is a Pauli-paramagnetic metal. [ABSTRACT FROM AUTHOR]

The compound Sr3LiAs2H was synthesized by reaction of elemental strontium, lithium, and arsenic, as well as LiH as hydrogen source. The crystal structure was determined by single-crystal X-ray diffraction: space group Pnma; Pearson symbol oP28; a = 12.0340(7), b = 4.4698(2), c = 12.5907(5) Å; V = 677.2(1) Å3; RF = 0.047 for 1021 reflections and with 36 parameters refined. The positions of the hydrogen atoms were first revealed by the electron localizability indicator and subsequently confirmed by crystal structure refinement. In the crystal structure of Sr3LiAs2H the metal atoms are arranged in a Gd3NiSi2-type motif, whereas the hydrogen atoms are arranged in a distorted tetrahedral environment formed by strontium. The calculated band structure revealed that Sr3LiAs2H is a semiconductor, which is in agreement with its diamagnetic behavior. Thus, Sr3LiAs2H is considered as a (charge-balanced) Zintl phase. [ABSTRACT FROM AUTHOR]

The electron density in a one-coordinate [GaIN(SiMe3)R] complex has been determined from ab initio calculations and multipole modeling of 90 K X-ray data. The topologies of the Laplacian distribution and the ELI-D match a situation having an sp3-hybridized nitrogen with a tetrahedral arrangement of two single σ-bonds (to carbon and silicon) and two lone pairs pointing towards gallium in a scissor-grasping fashion. The analysis of the Laplacian distribution furthermore reveals a ligand-induced charge concentration (LICC) in the outer core of gallium oriented directly towards the nitrogen atom, and thus in between the two lone pairs. These observations might suggest that the trigonal planar nitrogen geometry result from a dative GaN bond, in which the roles of the metal and the ligand have been reversed with respect to a 'standard' metal-ligand interaction, that is, the metal is here electron-donating. The ELI-D reveals a diffuse and directional lone pair on gallium, suggesting that this complex could serve as a σ-donor. [ABSTRACT FROM AUTHOR]

Complete miscibility of the intermetallic phases (IPs) SrGa2 and BaGa2 forming the solid solution Sr1− xBa xGa2 is shown by means of X-ray diffraction, thermoanalytical and metallographic studies. Regarding the distances of Sr/Ba sites versus substitution degree, a model of isolated substitution centres (ISC) for up to 10 % cation substitution is explored to study the influence on the Ga bonding situation. A combined application of NMR spectroscopy and quantum mechanical (QM) calculations proves the electric field gradient (EFG) to be a sensitive measure of different bonding situations. The experimental resolution is boosted by orientation-dependent NMR on magnetically aligned powder samples, revealing in first approximation two different Ga species in the ISC regimes. EFG calculations using superlattice structures within periodic boundary conditions are in fair agreement with the NMR spectroscopy data and are discussed in detail regarding their application on disordered IPs. [ABSTRACT FROM AUTHOR]

A new class of aluminum homocatenated compounds (Li nAl nH2 n+2) is proposed based on quantum chemical calculations. In these compounds, Al abstracts an electron from Li, becoming valence isoelectronic with C, Si, and Ge, thus mimicking respective structural features of Group 14 hydrides. Using the Coalescence Kick search program coupled with density functional theory calculations, we investigated the potential energy surfaces of Li2Al2H6 and Li3Al3H6. Then single-point-energy coupled-cluster calculations were performed for the lowest energy structures found. Indeed, the global minima established for Li2Al2H6 and Li3Al3H6 contain the Al2H62− and Al3H63− kernels, which are isostructural with ethane (C2H6), disilane (Si2H6), digermane (Ge2H6) and propane (C3H8), trisilane (Si3H8), trigermane (Ge3H8) molecules, respectively. Structural, energetic, and electronic characteristics of the Li2Al2H6 and Li3Al3H8 compounds are presented and the viability of their synthesis is discussed. [ABSTRACT FROM AUTHOR]

A new class of aluminum homocatenated compounds (Li nAl nH2 n+2) is proposed based on quantum chemical calculations. In these compounds, Al abstracts an electron from Li, becoming valence isoelectronic with C, Si, and Ge, thus mimicking respective structural features of Group 14 hydrides. Using the Coalescence Kick search program coupled with density functional theory calculations, we investigated the potential energy surfaces of Li2Al2H6 and Li3Al3H6. Then single-point-energy coupled-cluster calculations were performed for the lowest energy structures found. Indeed, the global minima established for Li2Al2H6 and Li3Al3H6 contain the Al2H62− and Al3H63− kernels, which are isostructural with ethane (C2H6), disilane (Si2H6), digermane (Ge2H6) and propane (C3H8), trisilane (Si3H8), trigermane (Ge3H8) molecules, respectively. Structural, energetic, and electronic characteristics of the Li2Al2H6 and Li3Al3H8 compounds are presented and the viability of their synthesis is discussed. [ABSTRACT FROM AUTHOR]

A comparative study of chemical bonding peculiarities in 1,2,4,5-tetrazine was carried out to test the performance of a recently developed invariom approach against a conventional charge density analysis of high-resolution X-ray diffraction data and quantum chemical calculations within the plane-wave functional theory. The amazing similarity between the intermolecular features thus obtained for this van der Waals crystal showed the invariom approximation to now emerge as a fast and convenient way towards reliable description of weak intermolecular interactions. [ABSTRACT FROM AUTHOR]

Cover Feature: In-Cage Interactions in the Clathrate Superconductor Sr8Si46 (Chem. Eur. J. 4/2020) Keywords: chemical bonding; clathrate; high-pressure synthesis; silicon; strontium Chemical bonding, clathrate, high-pressure synthesis, silicon, strontium. [Extracted from the article]

A theoretical prediction of a new class of stable aluminum homocatenated LinAlnH2n+2 compounds is reported by A. I. Boldyrev and co ‐ workers in their Communication on page 5307 ff. For the first time it has been shown that aluminum atoms are capable to homocatenate with the formation of alkane ‐ like species. The wizard shown in the center of the cover picture symbolizes a chemist synthesizing molecules of “aluminum homocatenated ethane and propane” based on the idea of electronic transmutation. [ABSTRACT FROM AUTHOR]