In this presentation we explore some common features of unusually long single carbon-carbon bonds and unusually short carbon-carbon intermolecular contacts. In the former category, the recent discovery of a molecule with a 2.04 Å long C-C bond by Kubo et al. (2021) is the record holder. At the other end of the scale, some pancake bonded radicals show intermolecular contact distances significantly below the van der Waals distance of 3.40 Å, the shortest record coming from the work of Miller et al. (2009) at 2.80 Å. Both types of these extreme boding situations involve connections between delocalized π-electron species. Using a combination of density functional theory and high level multireference wave function theory we find that the diradical characters of these extreme bonding situations are central in understanding the chemical bonding of these species. We discuss the difficulties of estimating the bond dissociation energy, and find practical ways to obtain these. We present molecular structures that display stretched equilibrium single bonds longer than 2.04 Å, and equilibrium intermolecular contacts that are shorter than 2.80 Å.

Unusually long single carbon-carbon bonds and unusually short carbon-carbon intermolecular contacts

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.