Constructing Stable π‐Dimers: Two Parallel Pancake π–π Bonds

• Published in: Chemistry : a European journal Vol. 24; no. 63; pp. 16919 - 16924
• Main Authors: Gao, Feng‐Wei, Zhong, Rong‐Lin, Xu, Hong‐Liang, Su, Zhong‐Min
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 13.11.2018
• Subjects: Aromaticity; Benzene; biphenalenyl biradicaloids; bonding orbitals; Bonding strength; Chemistry; Covalent bonds; Dimers; Interlayers; Molecular orbitals; Molecular structure; Monomers; Multifunctional materials; short interlayer distances; stability; two parallel π–π bonding; biphenalenyl biradicaloids; bonding orbitals; two parallel π-π bonding; short interlayer distances; stability
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201804598

Stable phenalenyl (PLY) radical π‐dimers still play an important role for new multifunctional materials owing to their intriguing molecular structure and unusual pancake π–π bonding mode. Herein, we design a new biphenalenyl biradicaloid (1) consisting of two PLYs and one benzene ring linkage tethered by single bonds, which presents an open‐shell character. Further, three π‐dimers (a1, b1, and c1) combined with 1 and conventional biphenalenyl biradicaloid (a, b, and c), which are capable of forming two staggered PLY dimers, exhibiting a short interlayer distance between the monomers. Interestingly, the analysis of the frontier molecular orbital reveals that two bonding orbitals, namely, the two highest occupied molecular orbitals (HOMO and HOMO−1) are doubly occupied. The results reveal that three π‐dimers display two parallel pancake bonds. Moreover, they have small diradical and tetraradical characters, large interaction energies, and strong aromaticity, which indicate the stability of these π‐dimers. The present work creates a new class of strong pancake bonding and might be utilized in devising an array of materials. Pancake bonds: A biphenalenyl biradicaloid that consists of two phenalenyls and one benzene ring linkage (1) were designed for building two parallel stacked π–π bonds. Interestingly, three π‐dimers (a1, b1, and c1) combined with 1 and conventional biphenalenyl biradicaloid (a, b, and c), which exhibit unusual two parallel pancake‐shaped π–π bonding.