华东理工大学刘培念、国家纳米科学中心裘晓辉小组的一项最新研究报道了选择性[2+2]环加成法在Au(111)表面合成梯状苯烯。相关论文于2021年8月16日发表在《美国化学会杂志》上。

研究人员报道了Au(111)表面通过脱卤[2+2]环加成法合成线性LP链，其中1,2,4,5-四溴-3,6-二甲苯前驱体中甲基的空间位阻提高了化学选择性和取向有序性。采用扫描隧道显微镜和非接触原子力显微镜相结合的方法，课题组测定了金属衬底和NaCl/Au(111)上LP链的原子结构和电子性质。

隧穿光谱测量揭示了NaCl层上链的带电状态，这一发现得到了密度泛函理论计算的支持，预测了聚合物LP链中存在间接能带和反铁磁性。

据悉，由苯和环丁二烯交替形成的梯形苯环(LPs)在溶液中的合成不超过五个单元。更长的聚合物LPs由于其稳定性差和不溶性，到目前为止尚未获得。

附：英文原文

Title: Ladder Phenylenes Synthesized on Au(111) Surface via Selective [2+2] Cycloaddition

Author: Deng-Yuan Li, Xia Qiu, Shi-Wen Li, Yin-Ti Ren, Ya-Cheng Zhu, Chen-Hui Shu, Xiao-Yu Hou, Mengxi Liu, Xing-Qiang Shi, Xiaohui Qiu, Pei-Nian Liu

Issue&Volume: August 16, 2021

Abstract: Ladder phenylenes (LPs) composed of alternating fused benzene and cyclobutadiene rings have been synthesized in solution with a maximum length no longer than five units. Longer polymeric LPs have not been obtained so far because of their poor stability and insolubility. Here, we report the synthesis of linear LP chains on the Au(111) surface via dehalogenative [2+2] cycloaddition, in which the steric hindrance of the methyl groups in the 1,2,4,5-tetrabromo-3,6-dimethylbenzene precursor improves the chemoselectivity as well as the orientation orderliness. By combining scanning tunneling microscopy and noncontact atomic force microscopy, we determined the atomic structure and the electronic properties of the LP chains on the metallic substrate and NaCl/Au(111). The tunneling spectroscopy measurements revealed the charged state of chains on the NaCl layer, and this finding is supported by density functional theory calculations, which predict an indirect bandgap and antiferromagnetism in the polymeric LP chains.

DOI: 10.1021/jacs.1c05586

Source: https://pubs.acs.org/doi/10.1021/jacs.1c05586