Extremely Long C-C Bonds Predicted beyond 2.0 Å

Eero J J Korpela; Jhonatas R Carvalho; Hans Lischka; Miklos Kertesz

doi:10.1021/acs.jpca.3c01209

Extremely Long C-C Bonds Predicted beyond 2.0 Å

J Phys Chem A. 2023 May 25;127(20):4440-4454. doi: 10.1021/acs.jpca.3c01209. Epub 2023 May 11.

Authors

Eero J J Korpela¹, Jhonatas R Carvalho², Hans Lischka², Miklos Kertesz¹

Affiliations

¹ Chemistry Department and Institute of Soft Matter, Georgetown University, 37th and O Streets, NW, Washington, District of Columbia 20057-1227, United States.
² Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, United States.

Abstract

A number of conjugated molecules are designed with extremely long single C-C bonds beyond 2.0 Å. Some of the investigated molecules are based on analogues to the recently discovered molecule by Kubo et al. These bonds are analyzed by a variety of indices in addition to their equilibrium bond length including the Wiberg bond index, bond dissociation energy (BDE), and measures of diradicaloid character. All unrestricted DFT calculations indicate no diradical character supported by high-level multireference calculations. Finally, N_FOD was computed through fractional orbital density (FOD) calculations and used to compare relative differences of diradicaloid character across twisted molecules without central C-C bonding and those with extremely elongated C-C bonds using a comparison with the C-C bond breaking in ethane. No example of direct C-C bonds beyond 2.4 Å are seen in the computational modeling; however, extremely stretched C-C bonds in the vicinity of 2.2 Å are predicted to be achievable with a BDE of 15-25 kcal mol^-1.