Synthesis of Disubstituted Carboxonium Derivatives of Closo-Decaborate Anion [2,6-B10H8O2CC6H5]-: Theoretical and Experimental Study

A comprehensive study focused on the preparation of disubstituted carboxonium derivatives of closo-decaborate anion [2,6-B₁₀H₈O₂CC₆H₅]^- was carried out. The proposed synthesis of the target product was based on the interaction between the anion [B₁₀H₁₁]^- and benzoic acid C₆H₅COOH. It was shown that the formation of this product proceeds stepwise through the formation of a mono-substituted product [B₁₀H₉OC(OH)C₆H₅]^-. In addition, an alternative one-step approach for obtaining the target derivative is postulated. The structure of tetrabutylammonium salts of carboxonium derivative ((C₄H₉)₄N)[2,6-B₁₀H₈O₂CC₆H₅] was established with the help of X-ray structure analysis. The reaction pathway for the formation of [2,6-B₁₀H₈O₂CC₆H₅]^- was investigated with the help of density functional theory (DFT) calculations. This process has an electrophile induced nucleophilic substitution (EINS) mechanism, and intermediate anionic species play a key role. Such intermediates have a structure in which one boron atom coordinates two hydrogen atoms. The regioselectivity for the process of formation for the 2,6-isomer was also proved by theoretical calculations. Generally, in the experimental part, the simple and available approach for producing disubstituted carboxonium derivative was introduced, and the mechanism of this process was investigated with the help of theoretical calculations. The proposed approach can be applicable for the preparation of a wide range of disubstituted derivatives of closo-borate anions.

Crystal Structure Survey and Theoretical Analysis of Bifurcated Halogen Bonds

The possibility that two Lewis bases can share a single halogen atom within the context of a bifurcated halogen bond (XB) is explored first by a detailed examination of the CSD. Of the more than 22,000 geometries that fit the definition of an XB (with X = Cl, Br, I), less than 2% are bifurcated. There is a heavy weighting of I in such bifurcated arrangements as opposed to Br, which prefers monofurcated bonds. The conversion from mono to bifurcated is associated with a smaller number of short contact distances, as well as a trend toward lesser linearity. The two XBs within a bifurcated system are somewhat symmetrical: the two lengths generally differ by less than 0.05 Å, and the two XB angles are within several degrees of one another. Quantum calculations of model systems reflect the patterns observed in crystals and reinforce the idea that the negative cooperativity within a bifurcated XB weakens and lengthens each individual bond.

Radicalradical chalcogen bonds: CSD analysis and DFT calculations

This manuscript reports a combination of crystallographic analysis (Cambridge Structural Database) and theoretical DFT calculations in chalcogen bonding interactions involving radicals in both the Ch bond (ChB) donor and acceptor. As a radical ChB acceptor (nucleophile) we have used benzodithiazolyl radical (BDTA) and as Ch bond donors (electrophile) we have used dithiadiazolyl and diselenadiazolyl radicals of the general formula p-X-C6F4-CNChChN (Ch = S, and Se). We have evaluated how the para substituent (X) affects the interaction energy, spin density and charge/spin transfer from the electron rich BDTA radical to the electron poor dichalcogenadiazolyl ring. The ability of the latter rings to form ChBs in the solid state has been examined by a comprehensive search in the CSD; several cases are used to exemplify the preferred geometric features of the complexes and they are compared with the theory. The molecular surface electrostatic potentials calculated for these ChB donors allow for a very precise rationalization of the self-assembly motifs most frequently adopted in the crystalline state and of their relative robustness.

Coordination of a Central Atom by Multiple Intramolecular Pnicogen Bonds

A central pnicogen Z atom (Z = Sb, As) is covalently attached to the O atom of three -O(CH₂)_nX chains where X represents either an aldehyde or amine group. The chain can fold around so that the basic X group can engage in a noncovalent pnicogen bond with the central Z. The formation of up to three pnicogen bonds is energetically favored. The amine appears to engage in stronger pnicogen bonds than does the aldehyde, and bonds to Sb are favored over As, but there is little dependence on the length of the chain. The formation of each successive pnicogen bond reduces the magnitude of the σ-holes surrounding the Z atom, which tends to weaken the attraction for the basic end of the chain.

Hydrogen vs. Halogen Bonds in 1-Halo-Closo-Carboranes

A theoretical study of the hydrogen bond (HB) and halogen bond (XB) complexes between 1-halo-closo-carboranes and hydrogen cyanide (NCH) as HB and XB probe has been carried out at the MP2 computational level. The energy results show that the HB complexes are more stable than the XBs for the same system, with the exception of the isoenergetic iodine derivatives. The analysis of the electron density with the quantum theory of atoms in molecules (QTAIM) shows the presence of a unique intermolecular bond critical point with the typical features of weak noncovalent interactions (small values of the electron density and positive Laplacian and total energy density). The natural energy decomposition analysis (NEDA) of the complexes shows that the HB and XB complexes are dominated by the charge-transfer and polarization terms, respectively. The work has been complemented with a search in the CSD database of analogous complexes and the comparison of the results, with those of the 1-halobenzene:NCH complexes showing smaller binding energies and larger intermolecular distances as compared to the 1-halo-closo-carboranes:NCH complexes.

Utilization of counter anions for charge transportation in the electrical device fabrication of Zn(ii) metal–organic frameworks

The present work reports the fabrication of anion-induced electrical devices with Zn(ii) metal–organic frameworks.