International Center for Materials Nanoarchitectonics, National Institute for Materials Science , 1-1, Namiki, Tsukuba, Ibaraki 305-0044, Japan.
PESTO, Japan Science and Technology Agency , 4-1-8, Honcho, Kawaguchi, Saitama 332-0012, Japan.
ACS Nano. 2017 Aug 22;11(8):8122-8130. doi: 10.1021/acsnano.7b02973. Epub 2017 Jul 19.
According to Hückel theory, an anti-aromatic molecule possessing (4n)π-electrons becomes unstable. Although the stabilization has been demonstrated by radialene-type structures-fusing aromatic rings to anti-aromatic rings-in solution, such molecules have never been studied at a single molecular level. Here, we synthesize a cyclobutadiene derivative, dibenzo[b,h]biphenylene, by an on-surface intramolecular reaction. With a combination of high-resolution atomic force microscopy and density functional theory calculations, we found that a radialene structure significantly reduces the anti-aromaticity of the cyclobutadiene core, extracting π-electrons, while the small four-membered cyclic structure keeps a high density of the total charge.
根据休克尔理论，具有（4n）π电子的反芳香分子变得不稳定。尽管已经通过在溶液中融合芳香环和反芳香环的薁型结构证明了这种稳定性，但这种分子从未在单个分子水平上进行过研究。在这里，我们通过表面内分子反应合成了一种环丁二烯衍生物，二苯并[b，h]联苯。通过高分辨率原子力显微镜和密度泛函理论计算的结合，我们发现薁型结构显著降低了环丁二烯核心的反芳香性，提取了π电子，而小四元环结构保持了总电荷的高密度。
