The bonding patterns in coronene are complicated and controversial as denoted by the lack of consensus of how its electronic structure should be described. Among the different proposed descriptions, the two most representative are those generated by Clar's aromatic π-sextet and adaptative natural density partitioning (AdNDP) models. Quantum-chemical calculations at the density functional theory level are performed to evaluate the model that gives a better representation of coronene. To this end, we analyse the molecular structure of coronene, we estimate the aromaticity of its inner and outer rings using various local aromaticity descriptors, and we assess its chemical reactivity from the study of the Diels-Alder reaction with cyclopentadiene. Results obtained are compared with those computed for naphthalene and phenanthrene. Our conclusion is that Clar's π-sextet model provides the representation of coronene that better describes the physicochemical behavior of this molecule. © 2017 Wiley Periodicals, Inc.
An in silico study is performed on the structure and the stability of noble gas (Ng) bound MO complexes (M = Cu, Ag, Au). To understand the stability of these Ng bound complexes, dissociation energies, dissociation enthalpy, and dissociation free energy change are computed. The stability of NgMO is also compared with that of the experimentally detected NgMX (X= F, Cl, Br). It is found that MO has lower Ng binding ability than that of MX. All the dissociation processes producing Ng and MO are endothermic in nature and for the Kr‐Rn bound MO (M = Cu, Au), and Xe and Rn bound AgO cases, the corresponding dissociation processes are turned out to be endergonic in nature at standard state. The Wiberg bond indices of NgM bonds and Ng→M electron transfer gradually increase from Ar to Rn and for the same Ng they follow the order of NgAuO > NgCuO > NgAgO. Energy decomposition analysis shows that the NgM bonds in NgMO are partly covalent and partly electrostatic in nature. Electron density analysis further highlights the partial covalent character in NgM bonds. © 2016 Wiley Periodicals, Inc.
Noble gas (Ng) binding ability of monocationic M-bipyridine (M = Cu, Ag, Au) complexes is investigated at the MPW1B95/cc-pVTZ/cc-pVTZ-PP level. While the bond dissociation energy, enthalpy change, and free energy change for the dissociation process are computed to assess the efficacy of the Ng binding ability of these complexes, topological analysis of electron density, natural bond orbital, and energy decomposition analyses are carried out to characterize the nature of NgÀM bonds. The range of NgÀM dissociation energy values is within 5.8-13.7 kcal/mol for Cu, 4.0-12.0 kcal/mol for Ag, and 5.5-19.7 kcal/mol for Au complexes with gradual increase in moving from Ar to Rn. For a given Ng, the Ng binding ability is highest for Au followed by Cu and Ag complexes, except for the Ar case. In all the cases, the KrÀRn dissociation processes from the respective bound complexes are endergonic in nature at room temperature. The interaction between Ng and M centers are supported dominantly by orbital and ionic interactions with almost equal contribution. The partial covalent nature of NgÀM bonds is also reflected in the topological analysis of electron density.[a] G.
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