Transferable Aspherical Atom Modeling of Electron Density in Highly Symmetric Crystals: A Case Study of Alkali-Metal Nitrates

A comparative electron density study (from X-ray diffraction and periodic quantum chemistry) of sodium and potassium nitrates is performed to test the performance of a transferrable aspherical atom model, which is based on the invarioms, to describe chemical bonding features of ions occurring in sites of different symmetry typical of inorganic salts and in different crystal environments. Relying on tabulated entries for the isolated ions (although tailor-made to account for different site symmetries), it takes the same time to employ as the spherical atom model routinely used in X-ray diffraction studies but provides an electron density distribution that faithfully reveals all the interionic interactionseven the weakest ones (such as between the nitrate anions or a K···N interaction found in the metastable form of KNO₃) yet important for properties of inorganic materialsas if obtained from high-resolution X-ray diffraction data

Extremely Long Cu···O Contact as a Possible Pathway for Magnetic Interactions in Na₂Cu(CO₃)₂

Chemical binding in a mixed copper sodium carbonate Na₂Cu­(CO₃)₂, a layered material showing ferromagnetic intralayer exchange and weak antiferromagnetic interlayer coupling, was examined within the topological analysis of experimental (from high-resolution X-ray diffraction) and theoretical (from periodic quantum chemical calculations) electron density functions in its crystal. Together with modeling of a superexchange pathway within the LSDA and DFT+U approach, the results obtained reveal a very weak Cu···O interaction (0.5 kcal/mol worth) between the copper–carbonate layers that is nevertheless stabilizing (bonding) and may serve as a possible pathway for antiferromagnetic interactions

Extremely Long Cu···O Contact as a Possible Pathway for Magnetic Interactions in Na₂Cu(CO₃)₂

Chemical binding in a mixed copper sodium carbonate Na₂Cu­(CO₃)₂, a layered material showing ferromagnetic intralayer exchange and weak antiferromagnetic interlayer coupling, was examined within the topological analysis of experimental (from high-resolution X-ray diffraction) and theoretical (from periodic quantum chemical calculations) electron density functions in its crystal. Together with modeling of a superexchange pathway within the LSDA and DFT+U approach, the results obtained reveal a very weak Cu···O interaction (0.5 kcal/mol worth) between the copper–carbonate layers that is nevertheless stabilizing (bonding) and may serve as a possible pathway for antiferromagnetic interactions

Radical Silyldifluoromethylation of Electron-Deficient Alkenes

A reaction of bromo- and iododifluoromethyl-substituted silanes with electron-deficient alkenes in the presence of an N-heterocyclic carbene borane complex is described. The reaction is performed under irradiation with light-emitting diodes and proceeds via a radical chain mechanism. The resulting products, the functionalized silicon reagents, can undergo chemoselective transformations involving either the silyldifluoromethyl fragment or the functional group

Theoretical QTAIM, ELI-D, and Hirshfeld Surface Analysis of the Cu–(H)B Interaction in [Cu₂(<i>bipy</i>)₂B₁₀H₁₀]

Interaction of [Cu₂B₁₀H₁₀] with 2,2′-bipyridine (<i>bipy</i>) afforded a novel binuclear discrete complex of the [Cu₂(<i>bipy</i>)₂B₁₀H₁₀] composition. Two copper­(I) atoms coordinate a bridge boron cage through an apical edge and a triangular BBB face situated at its opposite apical vertices to form four 3c2e (CuHB) and one 2c2e Cu–B bonds. The charge density model was obtained by density functional theory calculations of isolated molecule and crystal. The resultant densities were analyzed using the quantum theory of atoms in molecules (QTAIM) and electron localizability indicator (ELI-D). The geometry and the topological parameters of copper­(I) coordination environment were found to be sensitive to crystal-field effect. An annulus of flat electron density ρ­(<i>r</i>) and small ∇²ρ­(<i>r</i>) is formed at dianion faces. As a result, some of the expected B–B, Cu–B, or Cu–H bond critical points are absent. The topological instability in the region of multicentered bonds is observed. The Cu–B bonding was found to be presumably electrostatic in nature, which could be the reason of topological isomerism for copper­(I) decaborates. The results show that an unambiguous real-space criterion for multicentered bonding between transition metals and polyhedral boron anions is not yet given. The molecular graph for this class of compounds does not provide a definitive picture of the chemical boding and can be complemented with other descriptors, such as virial graphs and the ELI-D distribution

Geminal Silicon/Zinc Reagent as an Equivalent of Difluoromethylene Bis-carbanion

A new difluorinated reagent, [difluoro­(trimethylsilyl)­methyl]­zinc bromide, bearing C–Zn and C–Si bonds is described. The reagent is conveniently prepared by cobalt-catalyzed halogen/zinc exchange. It can be coupled with two different C-electrophiles in a stepwise manner (with allylic halides for C–Zn bond and aldehydes for C–Si bond) affording products containing a difluoromethylene fragment

Theoretical QTAIM, ELI-D, and Hirshfeld Surface Analysis of the Cu–(H)B Interaction in [Cu₂(<i>bipy</i>)₂B₁₀H₁₀]

Interaction of [Cu₂B₁₀H₁₀] with 2,2′-bipyridine (<i>bipy</i>) afforded a novel binuclear discrete complex of the [Cu₂(<i>bipy</i>)₂B₁₀H₁₀] composition. Two copper­(I) atoms coordinate a bridge boron cage through an apical edge and a triangular BBB face situated at its opposite apical vertices to form four 3c2e (CuHB) and one 2c2e Cu–B bonds. The charge density model was obtained by density functional theory calculations of isolated molecule and crystal. The resultant densities were analyzed using the quantum theory of atoms in molecules (QTAIM) and electron localizability indicator (ELI-D). The geometry and the topological parameters of copper­(I) coordination environment were found to be sensitive to crystal-field effect. An annulus of flat electron density ρ­(<i>r</i>) and small ∇²ρ­(<i>r</i>) is formed at dianion faces. As a result, some of the expected B–B, Cu–B, or Cu–H bond critical points are absent. The topological instability in the region of multicentered bonds is observed. The Cu–B bonding was found to be presumably electrostatic in nature, which could be the reason of topological isomerism for copper­(I) decaborates. The results show that an unambiguous real-space criterion for multicentered bonding between transition metals and polyhedral boron anions is not yet given. The molecular graph for this class of compounds does not provide a definitive picture of the chemical boding and can be complemented with other descriptors, such as virial graphs and the ELI-D distribution

Electrostatic Origin of Stabilization in MoS₂–Organic Nanocrystals

Negatively charged molybdenum disulfide layers form stable organic–inorganic layered nanocrystals when reacted with organic cations in solution. The reasons why this self-assembly process leads to a single-phase compound with a well-defined interlayer distance in given conditions are, however, poorly understood to date. Here, for the first time, we quantify the interactions determining the cation packing and stability of the MoS₂–organic nanocrystals and find that the main contribution arises from Coulomb forces. The study was performed on the series of new layered compounds of MoS₂ with naphthalene derivatives, forming several distinct phases depending on reaction conditions. Starting with structural models derived from powder X-ray diffraction data and TEM, we evaluate their cohesion energy by modeling layer separation with periodic PW-DFT-D calculations. The results provide a reliable approach for estimation of the stability of MoS₂-based heterolayered compounds

Cu(II)-Silsesquioxanes as Secondary Building Units for Construction of Coordination Polymers: A Case Study of Cesium-Containing Compounds

Five new bi- and trimetallic copper-organosilsesquioxanes {[VinSiO₂]₁₂­Cu₄Cs₄­(BuOH)₂­(EtOH)₂­(MeOH)}­·2BuOH (<b>1</b>), {[PhSiO₂]₁₂­Cu₄Cs₂K₂­(1,4-dioxane)₉­(H₂O)₂}­·3.4­(1,4-dioxane) (<b>2</b>), {[PhSiO₂]₁₂­Cu₄Cs₄­(DMF)₆}­·2DMF (<b>3</b>), {[MeSiO₂]₁₂­Cu₄Cs₄(THF)_4.5­(MeOH)₂­(H₂O)_0.25} (<b>4</b>), and {[MeSiO₂]₂₄­Cu₁₀Cs₆­(OH)₂­(THF)_4.2­(MeOH)_4.1­(H₂O)_0.7} (<b>5</b>) have been synthesized by an exchange reaction between discrete cage alkali,copper-siloxane and cesium chloride (<b>1</b>,<b> 2</b>) or cesium carbonate (<b>4</b>,<b> 5</b>) or by interaction of copper-phenylsiloxane with cesium phenylsiloxanolate (<b>3</b>). While in <b>1</b>–<b>4</b> the alkali,copper-silsesquioxane cage remains stable during reaction procedures, complex <b>5</b> was obtained by unexpected dimerization of two cages. The neutral cages act with solvent molecules and neighboring cages as square (<b>1</b>,<b> 3</b>,<b> 5</b>), tetrahedral (<b>4</b>), or octahedral (<b>2</b>) nodes giving, respectively, the two-periodic (2D) <b>sql</b> net, and the three-periodic (3D) <b>dia</b> or <b>pcu</b> nets. The roles of the cage structure, nature of metal atoms, and organic coating in the formation of one-, two-, and three-periodic coordination polymers are discussed in the example of newly synthesized and previously obtained alkali,copper-organosiloxanes and copper-organosiloxanes with sandwich or globular cage structures. What’s more, the charge distribution in crystals of <b>1</b>–<b>3</b> was analyzed by means of Bader’s Quantum Theory of Atoms-in-Molecules approach giving evidence of relatively strong bonding between neighboring cages

Stabilization of 1T-MoS₂ Sheets by Imidazolium Molecules in Self-Assembling Hetero-layered Nanocrystals

We report a facile, room-temperature assembly of MoS₂-based hetero-layered nanocrystals (NCs) containing embedded monolayers of imidazolium (Im), 1-butyl-3-methyl­imid­azolium (BuMeIm), 2-phenyl­imid­azolium, and 2-methyl­benz­imid­azolium molecules. The NCs are readily formed in water solutions by self-organization of the negatively charged, chemically exfoliated 0.6 nm thick MoS₂ sheets and corresponding cationic imidazole moieties. As evidenced by transmission electron microscopy, the obtained NCs are anisotropic in shape, with thickness varying in the range 5–20 nm and lateral dimensions of hundreds of nanometers. The NCs exhibit almost turbostratic stacking of the MoS₂ sheets, though the local order is preserved in the orientation of the imidazolium molecules with respect to the sulfide sheets. The atomic structure of NCs with BuMeIm molecules was solved from powder X-ray diffraction data assisted by density functional theory calculations. The performed studies evidenced that the MoS₂ sheets of the NCs are of the nonconventional 1T-MoS₂ (metallically conducting) structure. The sheets’ puckered outer surface is formed by the S atoms and the positioning of the BuMeIm molecules follows the sheet nanorelief. According to thermal analysis data, the presence of the BuMeIm cations significantly increases the stability of the 1T-MoS₂ modification and raises the temperature for its transition to the conventional 2H-MoS₂ (semiconductive) counterpart by ∼70 °C as compared to pure 1T-MoS₂ (∼100 °C). The stabilizing interaction energy between inorganic and organic layers was estimated as 21.7 kcal/mol from the calculated electron density distribution. The results suggest a potential for the design of few-layer electronic devices exploiting the charge transport properties of monolayer thin MoS₂