Does the Presence of a Bond Path Really Mean Interatomic Stabilization? The Case of the Ng@Superphane (Ng = He, Ne, Ar, and Kr) Endohedral Complexes

Using a fairly structurally flexible and, therefore, very suitable for this type of research, superphane molecule, we demonstrate that the inclusion of a noble gas atom (Ng = He, Ne, Ar, and Kr) inside it and, thus, the formation of the Ng@superphane endohedral complex, leads to its ‘swelling’. Positive values of both the binding and strain energies prove that encapsulation and in turn ‘swelling’ of the superphane molecule is energetically unfavorable and that the Ng⋯C interactions in the interior of the cage are destabilizing, i.e., repulsive. Additionally, negative Mayer Bond Orders indicate the antibonding nature of Ng⋯C contacts. This result in combination with the observed Ng⋯C bond paths shows that the presence of a bond path in the molecular graph does not necessarily prove interatomic stabilization. It is shown that the obtained conclusions do not depend on the computational methodology, i.e., the method and the basis set used. However, on the contrary, the number of bond paths may depend on the methodology. This is yet another disadvantageous finding that does not favor the treatment of bond paths on molecular graphs as indicators of chemical bonds. The Kr@superphane endohedral complex features one of the longest C–C bonds ever reported (1.753 Å).

A theoretical study on the adsorption of dichlorodiphenyltrichloroethane (DDT) on graphitic carbon nitride (g-C3N4) and g-C3N4 modified with cluster Ni2

A robust and accurate tight-binding quantum chemical method was performed to study adsorption process of dichlorodiphenyltrichloroethane (DDT) on graphitic carbon nitride (g-C3N4) and g-C3N4 modified with nickel cluster (Ni2). The adsorption energy, charges on atoms, bond orders have been calculated and analysed. The obtained results indicate that the adsorption of DDT on the pristine g-C3N4 is physical of nature. Ni2 cluster can be easily doped on g-C3N4 due to the formation of chemical bonds. The Ni2-g-C3N4 system exhibits enhanced adsorption ability for DDT.

Quantum Mechanical Investigation of the Oxidative Cleavage of the C–C Backbone Bonds in Polyethylene Model Molecules

Recalcitrant plastic waste has caused serious global ecological problems. There is an urgent need to develop environmentally friendly and efficient methods for degrading the highly stable carbon skeleton structure of plastics. To that end, we used a quantum mechanical calculation to thoroughly investigate the oxidative scission of the carbon-carbon (C–C) backbone in polyethylene (PE). Here, we studied the reaction path of C–C bond oxidation via hydroxyl radical in PE. The flexible force constants and fuzzy bond orders of the C–C bonds were calculated in the presence of one or more carbocations in the same PE carbon chain. By comparison, the strength of the C–C bond decreased when carbocation density increased. However, the higher the density of carbocations, the higher the total energy of the molecule and the more difficult it was to be generated. The results revealed that PE oxidized to alcohol and other products, such as carboxylic acid, aldehyde and ketone, etc. Moreover, the presence of carbocations was seen to promote the cleavage of C–C backbones in the absence of oxygen.

Atomic Charges, Surface Electrostatic Potential Analysis, and Bond Order Analysis on Nitriles and Isocyanides

Isocyanide-nitrile rearrangement has long been a continuing and interesting topic. A series of nitriles and isocyanides with the substituents of R=-AlH2, -BeH, -BH2, -C ≡ CH, -CF3, -CH3, -Cl, -C ≡ N, -COOH, -F, -H, Li, -MgH, -Na, -NH2, -NO2, -OH, -PH2, -SH, -SiH3, -CH = CH2 were investigated systematically based on full optimization at B3LYP-D3(BJ)/def2-QZVP level, and the isomerization energies from R-C ≡ N to :C = N-R were estimated. The substituent effect and bonding characters were analyzed by surface ESP colored van der Waals surfaces in conjunction with the global and local electrostatic extrema, the population analyses in terms of Hirshfeld and ADCH atomic charges, and bond order analyses via Laplacian and fuzzy bond orders.

Theoretical Studies of DENOx SCR over Cu-, Fe- and Mn-FAU Catalysts

Ab initio calculations based on the density functional theory were used. A cluster model of the faujasite zeolite structure (Al2Si22O66H36) with metal particles adsorbed above the aluminium centres was used. The NO and NH3 adsorption processes, individual and co-adsorption, have been studied over metal nanoparticles bound into zeolite clusters. Several configurations, electronic structure (charges, bond orders) and vibration frequencies have been analyzed to determine feasible pathways for the deNOx reaction. The M2O dimers (M = Cu, Mn or Fe) were considered in relation to the previous studies of iron complexes.