Ab initio prediction of Boron compounds arising from Borozene: Structural and electronic properties

Structure and electronic properties of two unusual boron clusters obtained by fusion of borozene rings has been studied by means of first principles calculations, based on the generalized-gradient approximation of the density functional theory, and the semiempirical tight-binding method was used for the transport calculations. The role of disorder has also been considered with single vacancies and substitutional atoms. Results show that the pure boron clusters are topologically planar and characterized by (3c-2e) bonds, which can explain, together with the aromaticity (estimated by means of NICS), the remarkable cohesive energy values obtained. Such feature makes these systems competitive with the most stable boron clusters to date. On the contrary, the introduction of impurities compromises stability and planarity in both cases. The energy gap values indicate that these clusters possess a semiconducting character, while when the larger system is considered, zero-values of the density of states are found exclusively within the HOMO-LUMO gap. Electron transport calculations within the Landauer formalism confirm these indications, showing semiconductor-like low bias differential conductance for these stuctures. Differences and similarities with Carbon clusters are highlighted in the discussion.Comment: 10 pages, 2 tables, 5 figure

The Ions MCp2+^{2+} (M = Sc, La): Significantly Bent Sandwich Species

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What is the preferred structure of the Meisenheimer-Wheland complex between sym-triaminobenzene and 4,6-dinitrobenzofuroxan?

The geometries, energies, and electronic properties of possible configurations of Meisenheimer-Wheland (M-W) complexes of sym-triaminobenzenes and 4,6-dinitrobenzofuroxan (DNBF) were investigated theoretically by MP2 and a variety of DFT methods. The pi-pi complex is preferred thermodynamically by more than 15 kcal/mol over the sigma-complexes for the unsubstituted species. However, the N-substituents of the 1,3,5-triaminobenzenes influence the relative stabilities of the alternative configurations significantly. The sigma-syn configuration of the M-W complex of 1,3,5-tris(N-piperidyl)benzene and DNBF has the lowest energy, followed closely by the sigma-anti and pi-pi forms. The small energy differences between different configurations are consistent with the dynamic interconversion of three homomeric structures observed experimentally by NMR. The ca. 1.63 A C-C interring bond exchanges among three equivalent sites. Quantum theory of atoms in molecules (QTAIM) analysis provided insights into the nature of the intermonomer interactions. Charge transfer and sigma bonding account for the stability and remarkably large binding energies of the M-W complexes

Preparation of [5,6]- and [6,6]-oxahomofullerene derivatives and their interconversion by lewis acid assisted reactions of fullerene mixed peroxides

[60]Fullerene mixed peroxides C-60(O)(OOtBu)(4) exhibit chemoand regioselective reactions under mild conditions. The epoxy moiety is opened by ferric chloride to form vicinal hydroxy chloride C60Cl(OH)(OOtBu)-BF3 is also effective in opening the epoxy moiety. The O-O bond of the fullerene mixed peroxide is cleaved by both [5,6]- and type aluminum chloride to form and [6,6]-fullerene hemiketals (oxohomo[60]fullerenes). A Hocktype rearrangement is proposed for the formation of the hemiketals, in which a fullerene C-C bond is cleaved. Lewis acids and/or visible light can initiate isomerization of the hemiketal isomers. Single-crystal X-ray analysis and theoretical calculations confirmed the results.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000231771700029&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Chemistry, MultidisciplinarySCI(E)EIPubMed36ARTICLE185449-54561