Pentaatomic planar tetracoordinate carbon molecules [XCAl3]q [(X,q) = (B,−2), (C,−1), (N,0)] with C–X multiple bonding

Abstract

Among the fascinating planar tetracoordinate carbon (ptC) species, pentaatomic molecules belong to the smallest class, well-known as "pptC". It has been generally accepted that the planarity of pptC structure is realized via the "delocalization" of the p(z) lone pair at the central carbon and the ligand-ligand bonding interaction. Although "localization" is as key driving force in organic chemistry as "delocalization", the "localization" concept has not been applied to the design of pptC molecules, to the best of our knowledge. In this paper, we apply the "localization" strategy to design computationally a series of new pptC. It is shown that the central carbon atom and one "electronegative" ligand atom X (compared to the Al ligand) effectively form a highly localized C-X multiple bond, converting the lone pair at the central carbon to a two-center two-electron π-bond. At the aug-cc-pVTZ-B3LYP, MP2 and CCSD(T) levels, the designed 18-valence-electron pptC species [XCAl(3)](q); [(X,q) = (B,-2), (C,-1), (N,0)] are found to each possess a stable ptC structure bearing a C-X double bond, indicated by the structural, molecular orbital, Wiberg bonding, potential energy surface and Born-Oppenheimer molecular dynamics (BOMD) analysis. Moreover, our OVGF calculations showed that the presently disclosed (yet previously unconsidered) pptC structure of [C(2)Al(3)](-) could well account for the observed photoelectron spectrum (previously only ascribed to a close-energy fan-like structure). Therefore, [C(2)Al(3)](-) could be the first pptC that bears the highly localized C-X double bond that has been experimentally generated. Notably, the pptC structure is the respective global minimum point for [BCAl(3)](2-) and [NCAl(3)], and the counterion(s) would further stabilize [BCAl(3)](2-) and [C(2)Al(3)](-). Thus, these newly designed pptC species with interesting bonding structure should be viable for future experimental characterization. The presently applied "localization" approach complements well the previous "delocalization" one, indicating that the general "localization vs. delocalization" concept in organic chemistry can be effectively transplanted to exotic pptC chemistry.

Planar tetracoordinate carbons with a double bond in CAl3E clusters

“…Cui et al coined the term ''unbalanced'' ligand environment in order to explain the localization in CAl 3 N. 16 The substitution of N by other group 15 elements also induces an ''unbalanced'' environment, leading to the formation of a CQE double bond in these 18 valence electron ptC species. These ptC clusters are both thermodynamically and kinetically viable species in the gas phase.…”

“…[2][3][4][5][6] In 1991, Schleyer and Boldyrev suggested a couple of pentaatomic clusters containing a ptC atom (cis-CSi 2 Al 2 and trans-CSi 2 Al 2 ). 16 Given the difference in electronegativities, an electron density localization between C and N is induced, leading to the formation of a double CQN bond. 8 In 2000, the groups of Wang and Boldyrev detected the CAl 4 Na À cluster in the gas phase.…”

Unraveling the Hydrogen Evolution Reaction Active Sites in N‐Functionalized Interconnected Graphene Quantum Dots

“…[2] Other electro-catalysts like metal chalcogenides, phosphides, carbides and borides (MoS 2 , Mo 2 C, WS 2 , WP 2 , CoSe 2 , CoB, Co 2 B, Ni 2 P, NiSe etc) appear in the next place after noble metals like Pt, Rh, Ru etc. [1,[3][4][5][6][7][8][9][10][11][12][13] The other types of catalysts are mainly the carbon based materials like g-C 3 N 4 , graphene and its derivatives. [14][15][16] However, the problems with the noble metals are associated with high cost and catalyst poisoning.…”

DEEM, a versatile platform of FRD measurement for highly multiplexed fibre systems in astronomy

“…Optical fibres are now widely used in astronomy. Introducing fibres into the large scale telescope makes it more efficient for multi-object survey with large field of view (FOV) (Angel et al 1977), such as SDSS (York et al 2000), AAT (Lewis et al 2002), LAMOST (Cui et al 2012) , DESI (Flaugher & Bebek 2014) and Subaru (Sugai et al 2015). But the nonconservation of the optical etendue that enlarges the solid angle of the output spot in the output end, which is known as focal ratio degradation (FRD), and the transmission efficiency limit the energy utilisation and decrease the signalto-noise ratio (SNR) of spectra especially in high-resolution spectrographs and highly multiplexed fibre systems (Grupp E-mail: yxyan@nao.cas.cn (Y. Yan) 2003; Feger et al 2012;Wang 2013).…”