Boron/Nitrogen Substitution of the Central Carbon Atoms of the Biphenalenyl Diradical π Dimer: A Novel 2e–12c Bond and Large NLO Responses
✍ Scribed by Dr. Rong-Lin Zhong; Dr. Ji Zhang; Dr. Shabbir Muhammad; Dr. Yang-Yang Hu; Dr. Hong-Liang Xu; Prof. Zhong-Min Su
- Publisher
- John Wiley and Sons
- Year
- 2011
- Tongue
- English
- Weight
- 869 KB
- Volume
- 17
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
Abstract
On the basis of the famous staggered biphenalenyl diradical π dimer 1, the eclipsed biphenalenyl (1 a), with no centrosymmetry, was obtained by rotating a layer of 1 by 60° around its central axis. Furthermore, the central carbon atoms of 1 and 1 a were substituted by boron and nitrogen atoms to form 2 and 2 a with a novel 2e–12c bond. We found that the novel 2e–12c bond is formed by the electron pair of the occupied orbital of the phenalenyl monomer substituted by the nitrogen atom and the unoccupied orbital of the phenalenyl monomer substituted by the boron atom. As a result of the novel 2e–12c bond, 2 and 2 a exhibit a fascinating interlayer charge‐transfer transition character, which results in a significant difference in the dipole moments (Δ__μ__) between the ground state and the crucial excited state. The values of Δ__μ__ for 2 and 2 a are 6.4315 and 6.9253 Debye, clearly larger than the values of 0 and 0.0015 Debye for 1 and 1 a. Significantly, the boron/nitrogen substitution effect can greatly enhance the first hyperpolarizabilities (β~0~) of 2 and 2 a with a novel 2e–12c bond compared with 1 and 1 a with a traditional 2e–12c bond: 0 and 19 a.u. for 1 and 1 a are much lower than 3516 and 12272 a.u. for 2 and 2 a. Furthermore, the interaction energies (E~int~)of 2 and 2 a are larger than those of 1 and 1 a, which could be considered as a signature of reliability for the newly designed dimers. Our present work will be beneficial for further theoretical and experimental studies on the properties of molecules with the novel 2e–12c bond.