CAl4Mg0/−: Global Minima with a Planar Tetracoordinate Carbon Atom

Abstract

Isomers of CAl4Mg and CAl4Mg− have been theoretically characterized for the first time. The most stable isomer for both the neutral and anion contain a planar tetracoordinate carbon (ptC) atom. Unlike the isovalent CAl4Be case, which contains a planar pentacoordinate carbon atom as the global minimum geometry, replacing beryllium with magnesium makes the ptC isomer the global minimum due to increased ionic radii of magnesium. However, it is relatively easier to conduct experimental studies for CAl4Mg0/− as beryllium is toxic. While the neutral molecule containing the ptC atom follows the 18 valence electron rule, the anion breaks the rule with 19 valence electrons. The electron affinity of CAl4Mg is in the range of 1.96–2.05 eV. Both the global minima exhibit π/σ double aromaticity. Ab initio molecular dynamics simulations were carried out for both the global minima at 298 K for 10 ps to confirm their kinetic stability.

From Molecules with a Planar Tetracoordinate Carbon to an Astronomically Known C5H2 Carbene

“…Despite all these experimental evidence, our recent theoretical studies have predicted that three singlet polar carbenes, bent-pentadiynylidene ( 4 ), buta-1,3-diynylcarbene ( 6 ), and 2-methylenebicyclo[1.1.0]­but-1(3)-en-4-ylidene ( 9 ), are yet to be identified in the laboratory. , Thus, further theoretical exploration of C 5 H 2 isomers became a natural prerequisite. Here, our prime focus is on two molecules, (SP-4)-spiro[2.2]­pent-1,4-dien-1,4-diyl ( 11 ) and (SP-4)-spiro[2.2]­pent-1,4-dien-1,5-diyl ( 13 ), that contain a planar tetracoordinate carbon (ptC) atom. − Though molecules with a ptC atom deviate from the traditional aspects of the tetrahedral tetracoordinate nature of carbon, which is one of the cornerstones of organic chemistry, tremendous interest has been paid by both experimentalists − and theoreticians − in this new class of molecules as they could potentially be used as new materials. With respect to C 5 H 2 , the relevance of isomers 11 and 13 in the formation of 2 is theoretically established here.…”

Why an integrated approach between search algorithms and chemical intuition is necessary?

“…39 However, this approach is computationally quite expensive for larger elemental compositions like C 12 O 2 Mg 2 . Of course, from our previous studies of small clusters such as CAl 4 Mg −/0 64 and BAl 4 Mg −/0/+ , 65 we realized that it does not guarantee all possible low-lying isomers although global minimum can be found unequivocally.…”

CSinGe4−n2+(n= 1–3): prospective systems containing planar tetracoordinate carbon (ptC)

“…Another most recent study shows that the global minimum structures of CAl 4 Mg 0/− have a ptC, and the systems are kinetically stable and have σ/π-dual aromaticity. 43 The neutral system has 18, and the anionic system has 19 valence electrons. Apart from the 18 valence electronic systems, many systems have a ptC without the presence of 18 valence electrons.…”