Embedding a Planar Hypercoordinate Carbon Atom into a [4n+2] π‐System

Abstract

Through delicate tuning of the electronic structure, we report herein a rational design of seventeen new putative global minimum energy structures containing a planar tetra‐ or pentacoordinate carbon atom embedded in an aromatic hydrocarbon. These structures are the result of replacing three consecutive hydrogen atoms of an aromatic hydrocarbon by less electronegative groups, forming a multicenter σ‐bond with the planar hypercoordinate carbon atom and participating in the π‐electron delocalization. This strategy that maximizes both mechanical and electronic effects through aromatic architectures can be extended to several molecular combinations to achieve new and diverse compounds containing planar hypercoordinate carbon centers.

Flat crown ethers with planar tetracoordinate carbon atoms

“…[ 29 ] The first crystallographically characterized ptC molecule, a divanadium complex, identified by Cotton and Miller, [ 30 ] was recognized later by Keese. [ 4 ] It is also noted here that molecules with a planar hypercoordinate carbon (phC) [ 7,31–42 ] atom are also actively pursued. Apart from the chemical bonding perspective, interest in molecules with a ptC or phC atom stems from the fact that they could be used as potential new materials.…”

Searching for double σ- and π-aromaticity in borazine derivatives

“…We used an initial population of 5X (X ¼ number of atoms of the system), this small population showed to be enough to successfully identify the lowest energy structures of many clusters and molecules. [39][40][41][42][43] Additionally, we evaluated the dynamic behavior of compounds 4, 6 and 8 (for an insight into their kinetic stability), employing Born-Oppenheimer molecular dynamic (BOMD) simulations. 44 Geometry optimizations, vibrational frequency and BOMD calculations were carried out using the Gaussian 16 program.…”

Analysis of Local and Global Aromaticity in Si₃C₅ and Si₄C₈ Clusters. Aromatic Species Containing Planar Tetracoordinate Carbon

“…Previously, some of the authors of this work had designed a series of ptC global minima composed of carbon and heavier atoms of group 14 of the periodic table [63][64][65]. The design strategy consisted of replacing three consecutive protons from an aromatic hydrocarbon by one E2 4+ fragment (E=Si-Pb), favoring the preservation of the -aromatic circuits of the parent aromatic hydrocarbons (see Scheme 1) [63].…”