Search

Carbene and its analogous silylene and germylene ligated trinuclear gold complexes are well established due to their cationic stability, but the anionic stability of such complexes is still rare. Density functional theory calculations on recently synthesized [Au3{C4H4(SiMe3)4Si}3]− and [Au3{C4H4(SiMe3)4Ge}3]− prove that the Au3 core is electron rich and the calculated vertical detachment energy is close to that of halogens. Further proper ligand manipulation on these complexes makes them remarkably stable anions having electron binding energies higher than 5 eV and behaving like superhalogens. Magnetic response calculations based on the magnetically induced current densities and the induced magnetic field confirm the aromatic nature of these anionic Au3-complexes. A study of the gradient Laplacian of electron density and energy density at the bond critical point and electron localization function gives additional bonding information of these anionic complexes. [ABSTRACT FROM AUTHOR]

The magnetically induced current–density susceptibility (MICD) of the [12]infinitene dianion and the induced magnetic field around it have been calculated at the density functional theory level. Separation of the MICD into diatropic and paratropic contributions shows that the MICD is dominated by the diatropic contribution in contrast to the notion that it is antiaromatic, which was reported in a recently published article. The MICD of the [12]infinitene dianion exhibits several through-space MICD pathways, whereas it sustains only weak local paratropic current-density contributions. We identified four main current-density pathways of which two are similar to the ones for neutral [12]infinitene. It is difficult to judge from calculations of the nucleus independent shielding constants and the induced magnetic field around the [12]infinitene dianion whether it sustains diatropic or paratropic ring currents. [ABSTRACT FROM AUTHOR]

Herein, the electronic structure and bonding character of the stable cyclo[18]carbon (C18) precursor, C18Br6, are thoroughly characterized by molecular orbital (MO), density of states (DOS), bond order (BO), and interaction region indicator (IRI) analyses. The delocalization characters of out‐of‐plane and in‐plane π‐electrons (labeled as πout‐ and πin‐electrons, respectively) in bonding regions were examined using localized orbital locator (LOL) and electron localization function (ELF). The aromaticity was investigated, studying the molecular magnetic response to external magnetic field by computing the magnetically induced current density (Jind), iso‐chemical shielding surface (ICSS), anisotropy of the induced current density (AICD), and the induced magnetic field (Bind). All these analyses indicate that C18Br6 is a globally aromatic species with lower aromaticity than C18, and the blocking of in‐plane π‐conjugation (labeled as πin‐conjugation) by the presence of ‐Br substituents in it is the underlying cause for the weakening of molecular aromaticity. [ABSTRACT FROM AUTHOR]

In this work, we analyzed the bonding and fluxional character of the global minimum of CAl11−. Its structure is formed by two stacked layers, one of them resembles the well-known planar tetracoordinate carbon CAl4 on top of a hexagonal Al@Al6 wheel. Our results show that the CAl4 fragment rotates freely around the central axis. The exceptional stability and fluxionality of CAl11− derive from its particular electron distribution. [ABSTRACT FROM AUTHOR]

How to build a molecular Helmholtz coil? The possibility to create a Helmholtz coil at the molecular level is studied via the induced magnetic responses of several small cyclic hydrocarbon dimers with formula (CnHn)2 and Dnh symmetry (n = 6–10). Our results reveal that for n ≥ 8, π-electrons give rise to a uniform magnetic field within the central region between rings, satisfying the Helmholtz coil condition. This uniformity is independent of the intensity of the induced magnetic field. [ABSTRACT FROM AUTHOR]

We systematically explore the potential energy surface of the B3Al4+ combination of atoms. The putative global minimum corresponds to a structure formed by an Al4 square facing a B3 triangle. Interestingly, the dynamical behavior can be described as a Reuleaux molecular triangle since it involves the rotation of the B3 triangle at the top of the Al4 square. The molecular dynamics simulations, corroborating with the very small rotational barriers of the B3 triangle, show its nearly free rotation on the Al4 ring, confirming the fluxional character of the cluster. Moreover, while the chemical bonding analysis suggests that the multicenter interaction between the two fragments determines its fluxionality, the magnetic response analysis reveals this cluster as a true and fully three-dimensional aromatic system. [ABSTRACT FROM AUTHOR]

In this work, we systematically explored clusters with formula B7M2− and B8M2 (M = Zn, Cd, Hg). The putative global minima are formed by an M2 dimer and a disk-shaped boron wheel. Moreover, the chemical bonding analysis revealed that charge transfer from the metal atoms to the boron motifs resulted in (B7)3−(M2)2+ and (B8)2−(M2)2+ complexes with double (σ + π) aromatic boron wheels and a single bond for the metallic dimer. Above all, the computed rotational barriers of the M–M fragment with respect to the boron disk and molecular dynamics simulations indicate a virtually barrierless spin, resembling a magnetic stirrer on a baseplate. [ABSTRACT FROM AUTHOR]

Helicenes consist of several fused rings twisted around an axis, forming a cylindrical helix, with π‐delocalized electrons in the non‐planar rings. Induced magnetic fields dissecting the orbital contributions of [6]‐, [7]‐, and [14]helicene are discussed. Computations show a deshielding cone produced by the π‐electrons along the helical axis. Unexpectedly, the response of the core electrons produces a shielding cone, which is cumulative and sensitive to the curvature of the systems owing to the overlap of the other ring responses. A warning is provided regarding the evaluation of the delocalization in curved systems in which the x‐ and y‐components of the induced magnetic field become relevant. [ABSTRACT FROM AUTHOR]

The putative global minimum of clusters with formula B10M2 (M = Rh, Ir) corresponds to icosahedral structures formed by two alternately stacked B5 rings with the metals located at the top and bottom vertices. These structures are the closest approximation of molecular clusters to the elusive icosahedral boron. A detailed analysis of the chemical bonding revealed that the covalent character between the transition metal and the boron framework as well as the strong delocalization throughout the structure enhances the stabilization of the icosahedral form. [ABSTRACT FROM AUTHOR]

Hyperconjugation and aromaticity are two of the most important concepts in chemistry. Mulliken and co‐workers combined both terms to explain the stability of cyclopentadiene. Here, we carried out DFT calculations on a series of mono‐ and disubstituted cyclopentadiene derivatives to investigate their hyperconjugative aromaticity. Our results revealed that one electropositive substituent can induce aromaticity, whereas one electronegative substituent prompts nonaromaticity rather than antiaromaticity. When an electronegative substituent and a transition metal as an electropositive substituent were considered simultaneously, a slightly aromatic cyclopentadiene ring could be achieved, whereas an electropositive substituent of the main group in combination with an electronegative one will produce a nonaromatic cyclopentadiene ring. One is enough:An electropositive substituent can induce hyperconjugative aromaticity, whereas an electronegative substituent (e. g. F) promotes nonaromaticity in monosubstituted cyclopentadienes. When both electropositive and electronegative substituents are considered simultaneously, the cyclopentadiene ring could be aromatic or nonaromatic, depending on the electropositive substituent. [ABSTRACT FROM AUTHOR]

Abstract: Herein we report the systematic exploration of the potential energy surfaces of a series of clusters with formula E5M7+ (E=C‐Pb and M=Li‐Cs). Fifteen of these combinations adopt a D5h three‐dimensional seven‐pointed star‐like structure in a singlet state, where M atoms interact electrostatically with the E5 ring. The determining factors in the relative preference of having the D5h structure over the most competitive isomer or vice‐versa are analyzed. These star‐shaped systems satisfy the 4n+2 Hückel's rule and exhibit a strong diatropic (σ and π) response to an external magnetic field. [ABSTRACT FROM AUTHOR]

Abstract: The structure, bonding, and stability of clusters with the empirical formula CE5− (E=Al–Tl) have been analyzed by means of high‐level computations. The results indicate that, whereas aluminum and gallium clusters have C2v structures with a planar tetracoordinate carbon (ptC), their heavier homologues prefer three‐dimensional C4v forms with a pentacoordinate carbon center over the ptC one. The reason for such a preference is a delicate balance between the interaction energy of the fifth E atom with CE4 and the distortion energy. Moreover, bonding analysis shows that the ptC systems can be better described as CE4−, with 17‐valence electrons interacting with E. The ptC core in these systems exhibits double aromatic (both σ and π) behavior, but the σ contribution is dominating. [ABSTRACT FROM AUTHOR]

We report a family of systems having a planar pentacoordinate carbon (ppC) based on the next heavier analogue of CAl5+, the ppC system par excellence. Although because of the larger size of Ga, the ppC isomer is not even a local minimum in CGa5+, a single isoelectronic substitution of Ga by smaller sized Be maximizes the bonding in the ppC form. Retaining the 18 valence electron rule, the global minimum structures of CGa4Be, CGa3Be2−, CGa2Be32−, and CGaBe43− clusters and their corresponding lithium salts have a ppC. [ABSTRACT FROM AUTHOR]

Correction for 'Structure and bonding of molecular stirrers with formula B7M2− and B8M2 (M = Zn, Cd, Hg)' by Rui Yu et al., Phys. Chem. Chem. Phys., 2020, 22, 12312–12320, https://doi.org/10.1039/D0CP01603A. [ABSTRACT FROM AUTHOR]