Thermodynamic studies of solute-solute and solute-solvent interactions in ternary aqueous systems containing {betaine + PEGDME250} and {betaine + K3PO4 or K2HPO4} at 298.15 K.

In this work, to evaluate solute-solute, solute-solvent and phase separation in aqueous systems containing {betaine + poly ethylene glycol dimethyl ether with molar mass 250 g mol-1 (PEGDME250)}, {betaine + K3PO4} and {betaine + K2HPO4}, first water activity measurements were made at 298.15 K and atmospheric pressure using the isopiestic technique. The water iso-activity lines of these three systems were obtained which have positive deviations from the semi-ideal solutions. This suggests that betaine-polymer and betaine-K3PO4 or betaine-K2HPO4 interactions are unfavorable; and these mixtures may form aqueous two-phase systems (ATPSs) at certain concentrations. Indeed the formation of ATPSs was observed experimentally. Then, osmotic coefficient values were calculated using the obtained water activity data; and, using the polynomial method the solute activity coefficients were determined. Using these activity coefficients, the transfer Gibbs energy ([Formula: see text]) values were calculated for the transfer of betaine from aqueous binary to ternary systems consisting polymer (PEGDME250) or salts (K3PO4 and K2HPO4). The obtained positive [Formula: see text] values again indicated that there is unfavorable interaction between betaine and these solutes. Finally, the volumetric and ultrasonic studies were made on these systems to examine the evidence for the nature of interactions between betaine and the studied salts or polymer.

A DFT study on NO reduction to N2O using Al- and P-doped hexagonal boron nitride nanosheets.

Using the dispersion-corrected DFT calculations, the catalytic reduction of NO molecules to N2O is investigated over Al- and P-doped hexagonal boron nitride nanosheets (h-BNNS). It is found that NO dissociation over both these surfaces needs a very large energy barrier, which indicates it cannot proceed at normal temperature. In contrast, the results show that NO molecules can be easily reduced into N2O via a dimer mechanism. The obtained activation energies reveal that the catalytic activity of Al-doped h-BNNS is better than that of P-doped one, mainly due to the moderate coadsorption energies of NO molecules over this surface.

A comparative DFT study on single-atom catalysis of CO oxidation over Al- and P-embedded hexagonal boron-nitride nanosheets.

Density functional theory calculations are performed to compare catalytic oxidation of CO molecule over Al- and P-embedded hexagonal boron nitride nanosheet (h-BN). It is found that the Al and P adatom can be stably anchored on the boron-vacancy site of h-BN, as evidenced by a relatively large adsorption energy and charge-transfer value. According to our findings, the oxidation of CO over these surfaces proceeds via the Langmuir-Hinshelwood mechanism, followed by the elimination of the remaining atomic O by another CO molecule. Meanwhile, the stronger adsorption of O2 than CO avoids poisoning of the active site of both surfaces. The results of the present study indicate that Al-doped h-BN exhibits higher catalytic activity for CO oxidation than P-doped one, which may provide a valuable guidance on design metal-free catalysts to remove toxic CO molecules.

The enhancing effect of a cation-π interaction on the cooperativity of halogen bonds: A computational study.

In this work, we investigate the effect of a cation-π interaction on the cooperativity of X⋯N halogen bonds in PhX⋯NCX⋯NH3 complexes, where Ph=phenyl and X=Cl, Br, I. Molecular geometries and interaction energies of the resulting complexes are studied at the MP2/aug-cc-pVDZ(-PP) computational level. The mechanism of the cooperativity between halogen bonds is analyzed using parameters derived from the noncovalent index, quantum theory of atoms in molecules and natural bond orbital methodologies. It is found that the divalent cations (Be2+, Mg2+) have a larger influence on the cooperativity of halogen bonds than monovalent ones (Li+, Na+). The formation of a cation-π interaction leads to strengthening of the halogen bonds, hence increases their cooperativity.

Cationic P⋯N interaction in XH3P(+)⋯NCY complexes (X=H, F, CN, NH2, OH; Y=H, Li, F, Cl) and its cooperativity with hydrogen/lithium/halogen bond.

The geometries, interaction energies and bonding properties of cationic pnicogen bond (CPB) interactions are studied in binary XH3P(+)⋯NCY (X=H, F, CN, NH2, OH; Y=H, Li, F, Cl) complexes by means of MP2/aug-cc-pVTZ calculations. Interaction energies of these binary complexes span a large range, from -16.36kcal/mol in (NH2)H3P(+)⋯NCF to -71.36kcal/mol in FH3P(+)⋯NCLi complex. The spin-spin coupling constant across P⋯N interaction depends considerably on the nature of X and Y substituents. The characteristic of CPB interactions is analyzed in terms of parameters derived from quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analyses. The charge transfer from the nitrogen base to the cationic acid stabilizes these pnicogen-bonded complexes. For a given XH3P(+), the net charge transfer value increases as the interaction energy of the complex becomes more negative, i.e., NCLi>NCCl>NCH>NCF. Moreover, mutual influence between the CPB and hydrogen/halogen/lithium bond is studied in the ternary XH3P(+)⋯NCY⋯NCH complexes. The results indicate that the formation of a Y⋯N interaction tends to strengthen CPB in the ternary systems.