Structures, stabilities and aromatic properties of endohedrally transition metal doped boron clusters M@B22, M = Sc and Ti: a theoretical study.

A genetic search algorithm in conjunction with density functional theory calculations was used to determine the lowest-energy minima of the pure B22 cluster and thereby to evaluate the capacity of its isomers to form endohedrally doped cages with two transition metal atoms M (M = Sc and Ti). An important charge transfer from metal atoms M to the boron cage takes place, stabilizing the endohedral compounds, as predicted with the genetic algorithm implemented. High-level coupled-cluster theory CCSD(T) calculations were carried out to confirm that the structures found are the lowest-energy isomers. For a deeper understanding of the doping effects and related charge transfer, the best structural motif of the B22 isomers was also determined when the bare cages are in anionic states, such as B222- and B224-. It was found that B22 has an appropriate size, geometric shape and electronic state to host the chosen metal atoms and, consequently, to form stable endohedrally doped compounds Ti@B22 (C2v, 4-Ti) and Sc@B22 (C2v, 5-Sc). The chemical bonding was analyzed in order to understand the molecular orbitals that these novel systems form. The cage aromaticity was evaluated by means of the nuclear independent chemical shift (NICS(0)iso) indices, the isochemical shielding surface (ICSSzz), the anisotropy of the current induced density (ACID) maps, and the magnetic ring current Gauge-Including Magnetically Induced Current (GIMIC) method, indicating that aromaticity plays a crucial role in the stabilization of endohedrally doped boron clusters. Finally, the thermodynamic stability of the latter, using parameters derived from density functional theory (DFT), was evaluated. Ab initio molecular dynamics (AIMD) simulations were performed to elucidate the stability, at high temperature, of the most stable endohedrally doped boron clusters 4-Ti and 5-Sc.

Erratum: Del Castillo, R.M., et al. Electronic Peculiarities of a Self-Assembled M12L24 Nanoball (M = Pd+2, Cr, or Mo). Molecules 2019, 24, 771.

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C50Cl10, a planar aromatic fullerene. Computational study of 13C-NMR chemical shift anisotropy patterns and aromatic properties.

The isolated-pentagon-rule (IPR) is a prime determinant of fullerene stabilization accounting for the difficult isolation of hollow Cn (n < 60) species. In this connection, the isolation and structural characterization of D5h-C50Cl10 as an IPR-violating fullerene are of interest owing to the study of factors providing further stability. Herein, we use DFT calculations to explore its aromatic behavior. In this connection the C50Cl10 structure is considered as a fullerene displaying a planar-aromatic character provided by the face-to-face disposition of two IPR structural motifs, mediated by ten exobonded sp3-carbons. In addition, the D5h-C50Br10 counterpart appears to be another promising structure as the target for explorative synthesis. Owing to the curvature of its IPR motif, an interesting variation in the 13C-NMR patterns relative to corannulene is described, where the relation between CI and CII signals is useful to evaluate the degree of the curvature of the π-surface. The charge distribution of C50Cl10 reveals a more electron-deficient IPR dome in comparison to C60, envisaging an enhanced chemistry related to bare fullerenes. In addition, the -Cl and -Br exobonded atoms provide effective σ-holes, suggesting such oblate fullerenes as interesting two-dimensional five-fold symmetric synthons useful for the formation of supramolecular species. Hence, an interesting chemistry and supramolecular array derivatives are potential applications to be further explored towards the development of novel nano-devices.

Hybridization vs. bond stretching isomerism in Ru(II) cyclometalated complexes of 2-phenylpyridine.

The phenomenon of formation of two isomers, yellow and orange, of the cyclometalated Ru(II) complex, [Ru(o-C6H4-py)(MeCN)4]⁺, was investigated by EELS spectroscopy and theoretical calculations. Both forms show very similar structures and spectroscopic properties, but slight differences in X-ray data and absorption between them were noted. No double minimum on the potential energy surface was found and thus these two forms cannot be considered as bond stretching isomers. However, the DFT study revealed the change in the hybridization of the carbon in trans-position of one of acetonitrile ligands. This effect can be responsible for the difference in colour. The results of the theoretical modelling coincide well with the experimental EELS data.

Oligomerization of 3,5-dimethyl benzyl alcohol promoted by clay: experimental and theoretical study.

Linear oligomerization of 3,5-dimethyl benzyl alcohol is induced by a montmorillonite clay (Tonsil Optimum Extra), producing 1,3,5,7-tetramethyl-9,10-dihydro-anthracene, which, by loss of protons results in the product 1,3,5,7-tetramethylanthracene. It was also found that the compounds 4-(3´,5´-dimethylbenzyl)-1,3,5,7-tetramethyl-9,10-dihydroanthracece and 4-(3´,5´-dimethylbenzyl)-1,3,5,7-tetra-methylanthracene were formed from 1,3,5,7-tetramethyl-9,10-dihydroanthracene. 1,3,5,7-Tetramethylanthryl radical cation was formed from 1,3,5,7-tetramethyl-9,10-dihydroanthracene; it was characterized by Electronic Paramagnetic Resonance (EPR). On the other hand, a theoretical analysis was performed, allowing the rationalization of the observed products and some of the key reaction steps.