Unexpected Charge Effects Strengthen π-Stacking Pancake Bonding

Zhong-Hua Cui; Meng-Hui Wang; Hans Lischka; Miklos Kertesz

doi:10.1021/jacsau.1c00272

Unexpected Charge Effects Strengthen π-Stacking Pancake Bonding

JACS Au. 2021 Aug 5;1(10):1647-1655. doi: 10.1021/jacsau.1c00272. eCollection 2021 Oct 25.

Authors

Zhong-Hua Cui^{1

2}, Meng-Hui Wang¹, Hans Lischka^{3

4}, Miklos Kertesz⁵

Affiliations

¹ Institute of Atomic and Molecular Physics, Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), Jilin University, Changchun 130012, P. R. China.
² Beijing National Laboratory for Molecular Sciences, Beijing 100190, P. R. China.
³ Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, United States.
⁴ A School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, P. R. China.
⁵ Chemistry Department and Institute of Soft Matter, Georgetown University, Washington, D.C. 20057-1227, United States.

Abstract

Phenalenyls (PLYs) are important synthons in many functional and electronic materials, which often display favorable molecule-to-molecule overlap for electron or hole transport. They also serve as a prototype for π-stacking pancake bonding based on two-electron multicenter bonding (2e/mc). Unexpected near-doubling of the binding energy is obtained for the positively charged PLY₂ ⁺ dimer with an effect similar to that seen for the positively charged olympicenyl (OPY) radical dimer. This charge effect is reversed for the perfluorinated (PF) dimers, and the negatively charged perfluorinated (PF) dimers PF-PLY₂ ^- and PF-OPY₂ ^- become strongly bound. Long-range interactions reflect these differences. Also surprising is that in this case the pancake bonding corresponds to single-electron (1e/mc) or a three-electron (3e/mc) multicenter bonding in contrast to the 2e/mc bonding that occurs for the neutral radical dimers. The strong preference for a large intermolecular overlap is maintained in these charged dimers. Importantly, the preference for π-bonding in the charged dimers compared to σ-bonding is strongly enhanced relative to the neutral PLY dimers.