Pancake π-π Bonding Goes Double: Unexpected 4e/All-Sites Bonding in Boron- and Nitrogen-Doped Phenalenyls.
Chemical bonding interactions are the main driving force for the formation of molecules and materials from atoms. The two-electron/multicenter pancake π-π bonding found in phenalenyl (PLY, 1) radical π-dimers is intriguing due to its unconventional nature of covalent bonding for molecular aggregations and its propensity to induce unique optical, electronic, and magnetic properties. By using high-level quantum chemistry calculations, we show that the B- or N-doped PLYs (2 and 4), usually considered closed-shell and therefore trifling, can be rendered open-shell singlet by proper edge substitutions (3 and 5). The resulting two unpaired valence electrons on each molecular unit contribute to the formation of a genuine pancake-shaped 4e/all-sites double π-π bonding upon intermolecular π-dimerization, in contrast to the 2e/half-sites single π-π bonding in the parent PLY π-dimers. The unusual double π-π bonding motif discovered in these PLY analogues may broaden the landscape of, and find new applications for, intermolecular covalent bonding interactions.
†College of Life Science, Research Center of Analytical Instrumentation, Key Laboratory of Bio-resource and Eco-environment of Ministry of Education, Sichuan University, Chengdu, Sichuan 610064, People's Republic of China.
Yong-Hui
YH
Tian
Bobby G
BG
Sumpter
§Division of Functional Materials and Nanodevices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Science, Ningbo, Zhejiang 315201, People's Republic of China.
Shiyu
S
Du
Jingsong
J
Huang
D001895:Boron / Q000737:chemistry*; D019281:Dimerization; D004583:Electrons; D008958:Models, Molecular; D008968:Molecular Conformation; D009584:Nitrogen / Q000737:chemistry*; D011789:Quantum Theory; D013816:Thermodynamics
D009584:Nitrogen; D001895:Boron
diradicaloid; p- or n-type doping; pancake π−π bonding; phenalenyl; van der Waals; π-dimerization