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Two new partially fluorinated dehydrobenzannulenes have been prepared by inter‐ and intramolecular oxidative homocoupling of diyne precursors. These systems contain fluorinated and nonfluorinated arene rings in a desymmetrized non‐alternant arrangement. Both macrocycles are roughly planar and organize into extended columns in the solid state. The assembly of these columns is mediated by the combination of dispersion interactions, slipped [π⋅⋅⋅π] stacking interactions of the perfluorinated rings with each other, and their association with the nonfluorinated rings in the molecules of the neighboring macrocycles. These results suggest that partial fluorination of dehydrobenzannulenes can serve as a versatile motif for their assembly into columnar superstructures. [ABSTRACT FROM AUTHOR]

Whether tetra‐tert‐butyl‐s‐indacene is a symmetric D2h structure or a bond‐alternating C2h structure remains a standing puzzle. Close agreement between experimental and computed proton chemical shifts based on minima structures optimized at the M06‐2X, ωB97X‐D, and M11 levels confirm a bond‐localized C2h symmetry, which is consistent with the expected strong antiaromaticity of TtB‐s‐indacene. [ABSTRACT FROM AUTHOR]

The physisorption-based separation of CO2 from CO is an energy-efficient yet challenging approach to obtain pure CO. We have applied an intrinsically porous molecular crystal (PMC), assembled from the readily synthesized macrocyclic cyclotetrabenzoin acetate to the problem of CO2/CO separation. This nanoporous material possesses both kinetic (micropore) and thermodynamic (CO2–π and CO2–carbonyl interactions) factors needed for selective CO2 capture. The moderate CO2–adsorbent interaction allows easy regeneration needed for pressure swing adsorption (PSA). Both trace (1%) and bulk (50%) amounts of CO2 can be removed from CO2/CO gas mixtures in PSA processes. [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]

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]

Abstract: An intriguing structural transition from the quasi‐planar form of B12 cluster upon the interaction with lithium atoms is reported. High‐level computations show that the lowest energy structures of LiB12, Li2B12, and Li3B12 have quasi‐planar (Cs), tubular (D6d), and cage‐like (Cs) geometries, respectively. The energetic cost of distorting the B12 quasi‐planar fragment is overcompensated by an enhanced electrostatic interaction between the Li cations and the tubular or cage‐like B12 fragments, which is the main reason of such drastic structural changes, resulting in the smallest tubular (Li2B12) and cage‐like (Li3B12) boron structures reported to date. [ABSTRACT FROM AUTHOR]

Two low-lying structures are unveiled for the Be6B11− nanocluster system that are virtually isoenergetic. The first, triple-layered cluster has a peripheral B11 ring as central layer, being sandwiched by two Be3 rings in a coaxial fashion, albeit with no discernible interlayer Be−Be bonding. The B11 ring revolves like a flexible chain even at room temperature, gliding freely around the Be6 prism. At elevated temperatures (1000 K), the Be6 core itself also rotates; that is, two Be3 rings undergo relative rotation or twisting with respect to each other. Bonding analyses suggest four-fold (π and σ) aromaticity, offering a dilute and fluxional electron cloud that lubricates the dynamics. The second, helix-type cluster contains a B11 helical skeleton encompassing a distorted Be6 prism. It is chiral and is the first nanosystem with a boron helix. Molecular dynamics also shows that at high temperature the helix cluster readily converts into the triple-layered one. [ABSTRACT FROM AUTHOR]

Whether tetra-tert-butyl-s-indacene is a symmetric D 2h structure or a bond-alternating C 2h structure remains a standing puzzle. Close agreement between experimental and computed proton chemical shifts based on minima structures optimized at the M06-2X, ωB97X-D, and M11 levels confirm a bond-localized C 2h symmetry, which is consistent with the expected strong antiaromaticity of TtB-s-indacene., (© 2023 Wiley-VCH GmbH.)

The putative global minimum of clusters with formula B 10 M 2 (M = Rh, Ir) corresponds to icosahedral structures formed by two alternately stacked B 5 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.

Herein we introduce a strategy employing lithium atoms as a scaffold to stabilize an embryo for boron tubes. The systematical exploration of the potential energy surface via evolutionary algorithms allowed us to find that Li2B24 adopts a tubular structure formed by three stacked rings of eight borons each with two lithium atoms capping the tube. The lithium atoms are essential for stabilization because of the strong electrostatic interaction between the Li cations and the boron framework, and concomitantly, they compensate for the energy cost of distorting a quasi-planar or double ring B24 cluster.

The structure, bonding, and stability of clusters with the empirical formula CE 5 - (E=Al-Tl) have been analyzed by means of high-level computations. The results indicate that, whereas aluminum and gallium clusters have C 2v structures with a planar tetracoordinate carbon (ptC), their heavier homologues prefer three-dimensional C 4v 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 CE 4 and the distortion energy. Moreover, bonding analysis shows that the ptC systems can be better described as CE 4 - , 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., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Two low-lying structures are unveiled for the Be 6 B 11 - nanocluster system that are virtually isoenergetic. The first, triple-layered cluster has a peripheral B 11 ring as central layer, being sandwiched by two Be 3 rings in a coaxial fashion, albeit with no discernible interlayer Be-Be bonding. The B 11 ring revolves like a flexible chain even at room temperature, gliding freely around the Be 6 prism. At elevated temperatures (1000 K), the Be 6 core itself also rotates; that is, two Be 3 rings undergo relative rotation or twisting with respect to each other. Bonding analyses suggest four-fold (π and σ) aromaticity, offering a dilute and fluxional electron cloud that lubricates the dynamics. The second, helix-type cluster contains a B 11 helical skeleton encompassing a distorted Be 6 prism. It is chiral and is the first nanosystem with a boron helix. Molecular dynamics also shows that at high temperature the helix cluster readily converts into the triple-layered one., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)