In Silico Analysis of the Aromaticity of Some -Metallabenzenes and -Dimetallabenzenes (-mers Proposed from Metallabenzenes).

In the current work, we introduce a novel class of molecules termed -metallabenzenes, and their aromaticity has been comprehensively analyzed. The molecules were strategically designed with the insertion of acetylene (C≡C or C) units in some selected metallabenzenes. Furthermore, if a second metallic unit is inserted (replacing a sp carbon) in the -metallabenzenes rings, a new family of -mers is generated, and this second group has been named as -dimetallabenzenes.

Exploration of the potential energy surface in mixed Zintl clusters applying an automatic Johnson polyhedra generator: the case of EM (E = Si, Ge, Sn; M = Sb, Bi).

A new algorithm called Automatic Johnson Cluster Generator (AJCG) is presented, which, as its name indicates, allows the definition of the desired Johnson polyhedron to subsequently carry out all the possible permutations between the atoms that form this polyhedron. This new algorithm allows the exhaustive study of the structures' potential energy surface (PES). In addition, the AJCG algorithm is helpful for the study of three-dimensional compounds such as boranes or Zintl clusters and their structural derivatives with two or more different atoms.

Core-electron contributions to the molecular magnetic response.

Orbital contributions to the magnetic response depend on the method used to compute them. Here, we show that dissecting nuclear magnetic shielding tensors using natural localized molecular orbitals (NLMOs) leads to anomalous core contributions. The arbitrariness of the assignment might significantly affect the interpretation of the magnetic response of nonplanar molecules such as C or [14]helicene and the assessment of their aromatic character.

Analysis in silico of chemical reactivity employing the local hyper-softness in some classic aromatic compounds, boron aromatic clusters and all-metal aromatic clusters.

In the current work, the authors analyzed and compared the chemical behavior of some (anti)aromatic compounds. The species selected are benzene and cyclobutadiene as the aromatic and antiaromatic classical examples, respectively. Next, the anion , which is the first all-metal molecule catalogued as aromatic and its non-metallic isoelectronic analog, were also analyzed.

Metallaborazines: To Be or Not To Be Delocalized.

In the current work, the analysis of the electronic delocalization of some metallacycles, based on borazine, was realized by employing magnetic criteria, such as the induced magnetic field and magnetically induced current densities, and electronic criteria, such as adaptative natural density partitioning and the analysis of molecular orbitals. The current metallaborazines were generated from isoelectronic substitutions. The main question is whether the electronic delocalization increases or decreases.

Correction to " Analysis of the Electronic Delocalization in Some Double Fused-Ring Metallabenzenes".

[This corrects the article DOI: 10.1021/acsomega.1c00632.

Analysis of the Electronic Delocalization in Some Double Fused-Ring Metallabenzenes.

In the current work, some metallabenzenes with one and several fused rings were analyzed in terms of their electronic delocalization. These fused-ring metallabenzenes are known as metallabenzenoids, and their aromatic character is not free of controversy. The systems of the current work were designed from crystallographic data of some synthesized molecules, and their electronic delocalization (aromaticity) was computationally examined in terms of the molecular orbital analysis (Hückel's rule), the induced magnetic field, and ring currents.

Delocalization in Substituted Benzene Dications: A Magnetic Point of View.

In this work, the induced magnetic field is analyzed for a series of substituted benzenes dications with formula CR (R=I, At, SeH, SeCH, TeH, TeCH), presumably exhibiting concentric aromaticity. Previous studies concluded that in the carbon skeleton, just π-electrons are delocalized. However, our results support that both the σ- and π-electrons are delocalized in the carbon skeleton, combined with a σ-delocalization in the external ring.

Analysis of the electronic delocalization in some isoelectronic analogues of B doped with beryllium and/or carbon.

In the current work, a new family of isoelectronic analogues to B12 is reported. The construction of this family was performed through the isoelectronic substitution principle to generate species such as B11C+, B11Be-, B10BeC, B10C22+, B10Be22- B9Be2C-, and B9BeC2+. The search for the global minimum was realized by utilizing genetic algorithms, while the induced magnetic field, electronic localization function, magnetic current densities, and multicenter aromaticity criteria were calculated to understand their electronic delocalization.

Revisiting the Rearrangement of Dewar Thiophenes.

The mechanism for the walk rearrangement in Dewar thiophenes has been clarified theoretically by studying the evolution of chemical bonds along the intrinsic reaction coordinates. Substituent effects on the overall mechanism are assessed by using combinations of the ring (R = H, CF) and traveling (X = S, S = O, and CH) groups. The origins of fluxionality in the S-oxide of perfluorotetramethyl Dewar thiophene are uncovered in this work.

Li7(BH)5(+): a new thermodynamically favored star-shaped molecule.

The potential energy surfaces (PESs) of Lin(BH)5(n-6) systems (where n = 5, 6, and 7) were explored using the gradient embedded genetic algorithm (GEGA) program, in order to find their global minima conformations. This search predicts that the lowest-energy isomers of Li6(BH)5 and Li7(BH)5(+) contain a (BH)5(6-) pentagonal fragment, which is isoelectronic and structurally analogous to the prototypical aromatic hydrocarbon anion C5H5(-). Li7(BH)5(+), along with Li7C5(+), Li7Si5(+) and Li7Ge5(+), joins a select group of clusters that adopt a seven-peak star-shape geometry, which is favored by aromaticity in the central five-membered ring, and by the preference of Li atoms for bridging positions.

Dynamical behavior of Borospherene: A Nanobubble.

The global minimum structure of borospherene (B40) is a cage, comprising two hexagonal and four heptagonal rings. Born-Oppenheimer Molecular Dynamics simulations show that continuous conversions in between six and seven membered rings take place. The activation energy barrier for such a transformation is found to be 14.

Planar tetracoordinate carbons with a double bond in CAl3E clusters.

The potential energy surfaces of a series of clusters with the formula CAl3E (E = P, As, Sb, Bi) are systematically explored using density functional theory and high level ab initio calculations. The global minimum structure of these clusters contains a planar tetracoordinate carbon atom. The presence of a C=E double bond is supported by the Wiberg bond indices, the adaptive natural density partitioning analysis, and the magnetic response.

Planar pentacoordinate carbons in CBe5(4-) derivatives.

The potential energy surfaces of a series of clusters with formula CBe5Lin(n-4) (n = 1 to 5) have been systematically explored. Our computations show that the lithium cations preserve the CBe5(4-) pentagon, such that the global minimum structure for these series of clusters has a planar pentacoordinate carbon (ppC) atom. The systems are primarily connected via a network of multicenter σ-bonds, in which the C atom acts as σ-acceptor and this acceptance of charge is balanced by the donation of the 2pz electrons to the π-cloud.

Stop rotating! One substitution halts the B19₁₉⁻ motor.

The B19(-) anion and other boron species have been dubbed 'Wankel motors' for the almost barrierless rotation of inner and outer concentric rings relative to each other in these compounds. A single substitution in B19(-) is shown to shut down the well-established fluxionality in the anion. A carbon atom substituted in the structure to give a neutral CB18 species is shown computationally to enforce bond localization.

Carbo-cages: a computational study.

Inspired by their geometrical perfection, intrinsic beauty, and particular properties of polyhedranes, a series of carbo-cages is proposed in silico via density functional theory computations. The insertion of alkynyl units into the C-C bonds of polyhedranes results in a drastic lowering of the structural strain. The induced magnetic field shows a significant delocalization around the three-membered rings.

B18(2-): a quasi-planar bowl member of the Wankel motor family.

A quasi-planar member of the so-called 'Wankel motor' family, B18(2-), is found. This boron cluster is an electronically stable dianion and a concentric doubly σ- and π-aromatic system. The inner B6 unit in B18(2-) undergoes quasi-free rotation inside the perimeter of the B12 ring.

Is Al2Cl6 aromatic? Cautions in superficial NICS interpretation.

In this article, we employed the induced magnetic field method to show that the Al2X6 (X = F, Cl, Br, I) clusters cannot be classified as aromatic systems. Interestingly, even nucleus independent chemical shift (NICS) reveals the same conclusion when analyzed in greater detail, showing that a superficial analysis of this index can easily lead to incorrect interpretations. In view of the fact that the NICS index is extensively used by computational and theoretically oriented experimental chemists, this is an important warning against superficial analyses, as it can lead to erroneous chemical interpretation.

Molecular structures of M2N2(2-) (M and N = B, Al, and Ga) clusters using the gradient embedded genetic algorithm.

Al(4)(2-) was the first discovered σ + π aromatic all-metal cluster. In the present work we analyze the molecular structure, relative stability, and aromaticity of lowest-lying isomers of related M(2)N(2)(2-) (M and N = B, Al, and Ga) clusters, with special emphasis devoted to the cis (C(2v)) and trans (D(2h)) isomers of the M(2)N(2)(2-) clusters. For such purpose, we start by performing the search of the global minimum for each cluster through the Gradient Embedded Genetic Algorithm (GEGA).

D3h CN3Be3+ and CO3Li3+: viable planar hexacoordinate carbon prototypes.

Searches for planar hexacoordinate carbon (phC) species comprised of only seven atoms uncovered good CX(3)M(3) prototypes, D(3h) CN(3)Be(3)(+) and CO(3)Li(3)(+). The latter is the global minimum. It might also be possible to detect the deep-lying kinetically-viable D(3h) CN(3)Be(3)(+) local minimum, based on its robustness toward molecular dynamic simulations and its very high isomerization barrier.

The induced magnetic field.

Aromaticity is indispensable for explaining a variety of chemical behaviors, including reactivity, structural features, relative energetic stabilities, and spectroscopic properties. When interpreted as the spatial delocalization of π-electrons, it represents the driving force for the stabilization of many planar molecular structures. A delocalized electron system is sensitive to an external magnetic field; it responds with an induced magnetic field having a particularly long range.

Starlike aluminum-carbon aromatic species.

Is it possible to achieve molecules with starlike structures by replacing the H atoms in (CH)(n)(q) aromatic hydrocarbons with aluminum atoms in bridging positions? Although D(4h) C(4)Al(4)(2-) and D(2) C(6)Al(6) are not good prospects for experimental realization, a very extensive computational survey of fifty C(5)Al(5)(-) isomers identified the starlike D(5h) global minimum with five planar tetracoordinate carbon atoms to be a promising candidate for detection by photoelectron detachment spectroscopy. BOMD (Born-Oppenheimer molecular dynamics) simulations and high-level theoretical computations verified this conclusion. The combination of favorable electronic and geometric structural features (including aromaticity and optimum C-Al-C bridge bonding) stabilizes the C(5)Al(5)(-) star preferentially.

CAl4Be and CAl3Be2(-): global minima with a planar pentacoordinate carbon atom.

Theoretical evidence for the first neutral and anionic global-minimum structures possessing a planar pentacoordinate carbon is reported.

Bonding, aromaticity, and structure of trigonal dianion metal clusters.

Various isomers of the trigonal dianion metal clusters, X(3)(2-), X = Be, Mg, Ca, and their mono- and disodium complexes are optimized at the B3LYP/6-311+G(d) level. Different conceptual density functional theory based reactivity descriptors as well as the induced magnetic field values are calculated to understand the stability and aromaticity of these systems. Possibility of bond stretch isomerism is explored.