Silicon carbide nanotubes (SiCNTs) serving for catalytic decomposition of toxic diazomethane (DAZM) gas: a DFT study

<p>In the present study, the adsorption and decomposition of diazomethane (DAZM) on the surface of (6,0) zigzag silicon carbide nanotube (SiCNT) are investigated using density functional theory calculations. The geometry structures of the three stable configurations, adsorption energies and electronic properties of DAZM adsorption on the surface of SiCNT are investigated. It was found that the DAZM molecule is decomposed over the surface of (6,0) SiCNT with activation energy (<i>E</i>_act) of 0.523 eV. The curvature effect on the adsorption energies of the DAZM molecule is also considered by studying (5,0) and (7,0) SiCNTs. The results display that DAZM adsorption over smaller diameter of SiCNT is thermodynamically more favourable than larger one.</p

Single Electron Pnicogen Bonded Complexes

A theoretical study of the complexes formed by monosubstituted phosphines (XH₂P) and the methyl radical (CH₃) has been carried out by means of MP2 and CCSD­(T) computational methods. Two minima configurations have been obtained for each XH₂P:CH₃ complex. The first one shows small P–C distances and, in general, large interaction energies. It is the most stable one except in the case of the H₃P:CH₃ complex. The second minimum where the P–C distance is large and resembles a typical weak pnicogen bond interaction shows interaction energies between −9.8 and −3.7 kJ mol^–1. A charge transfer from the unpaired electron of the methyl radical to the P–X σ* orbital is responsible for the interaction in the second minima complexes. The transition state (TS) structures that connect the two minima for each XH₂P:CH₃ complex have been localized and characterized

Symmetric bifurcated halogen bonds: substituent and cooperative effects

<p>The aim of this study is to investigate the geometries, interaction energies and bonding properties of the symmetrical bifurcated halogen bond interactions (BXBs) by means of <i>ab initio</i> calculations. For this purpose, the NCX (X = Cl, Br) molecule is paired with a series of N-formyl formamide (NFF) derivatives (NFF-Z, Z = H, CN, CCH, OH, CH₃ and Li), and the properties of the resulting complexes are studied by molecular electrostatic potential, quantum theory of atoms in molecules, noncovalent interaction index and natural bond orbital analyses. For a fixed NCX molecule, interaction energies increase in the order of Z = Li > CH₃ > H > OH > CCH > CN. We found a strong correlation between the interaction energies of NCX:NFF-Z complexes and molecular electrostatic potential minimum values associated with NFF-Z monomers. Moreover, cooperative effects between BXB and XċċċN halogen bond interactions are studied in the ternary NCX:NCX:NFF-Z systems. Our results indicate that the strength of BXB interactions in the ternary complexes is enhanced by the presence of XċċċN bonds. Besides, cooperativity effects tend to increase the covalency of BXBs in these systems.</p

Competition and Interplay between σ-Hole and π-Hole Interactions: A Computational Study of 1:1 and 1:2 Complexes of Nitryl Halides (O₂NX) with Ammonia

Quantum calculations at the MP2/cc-pVTZ, MP2/aug-cc-pVTZ, and CCSD­(T)/cc-pVTZ levels have been used to examine 1:1 and 1:2 complexes between O₂NX (X = Cl, Br, and I) with NH₃. The interaction of the lone pair of the ammonia with the σ-hole and π-hole of O₂NX molecules have been considered. The 1:1 complexes can easily be differentiated using the stretching frequency of the N–X bond. Thus, those complexes with σ-hole interaction show a blue shift of the N–X bond stretching whereas a red shift is observed in the complexes along the π-hole. The SAPT-DFT methodology has been used to gain insight on the source of the interaction energy. In the 1:2 complexes, the cooperative and diminutive energetic effects have been analyzed using the many-body interaction energies. The nature of the interactions has been characterized with the atoms in molecules (AIM) and natural bond orbital (NBO) methodologies. Stabilization energies of 1:1 and 1:2 complexes including the variation of the zero point vibrational energy (ΔZPVE) are in the ranges 7–26 and 14–46 kJ mol^–1, respectively