德国埃尔朗根-纽伦堡大学
n对位连接的苯烯形成闭环的[n]环对苯烯（[n]CPPs）因其独特的环结构和高效的对位共轭引起了人们极大的关注，从而产生了无数迷人的电子和光电性质。然而，它们的应变拓扑阻止了CPPs的π扩展，从而将其转换为扶手椅式纳米带或平面化的CPP大环。
该文中，研究人员成功地解决了这一长期存在的挑战，并通过低温扫描探针显微镜和光谱学结合密度泛函理论，介绍了Au（111）上原子精确平面内π扩展[12]CPP的自底向上合成和表征。平面π扩展CPP是一种具有全扶手椅边缘拓扑结构的纳米石墨烯。外围的排他性准共轭产生了离域电子态，而平面化最大化了p轨道的重叠，这两者都比传统的CPP减少了带隙。计算预测了双电荷系统中的环电流和整体芳香性。
有趣的平面环拓扑结构和独特的电子特性使平面π扩展CPPs成为一种很有前途的量子材料。
附：英文原文
Title: Planar π-extended cycloparaphenylenes featuring an all-armchair edge topology
Author: Xiang, Feifei, Maisel, Sven, Beniwal, Sumit, Akhmetov, Vladimir, Ruppenstein, Cordula, Devarajulu, Mirunalini, Drr, Andreas, Papaianina, Olena, Grling, Andreas, Amsharov, Konstantin Y., Maier, Sabine
Issue&Volume: 2022-06-27
Abstract: The [n]cycloparaphenylenes ([n]CPPs)—n para-linked phenylenes that form a closed-loop—have attracted substantial attention due to their unique cyclic structure and highly effective para-conjugation leading to a myriad of fascinating electronic and optoelectronic properties. However, their strained topology prevents the π-extension of CPPs to convert them either into armchair nanobelts or planarized CPP macrocycles. Here we successfully tackle this long-standing challenge and present the bottom-up synthesis and characterization of atomically precise in-plane π-extended [12]CPP on Au(111) by low-temperature scanning probe microscopy and spectroscopy combined with density functional theory. The planar π-extended CPP is a nanographene with an all-armchair edge topology. The exclusive para-conjugation at the periphery yields delocalized electronic states and the planarization maximizes the overlap of p orbitals, which both reduce the bandgap compared to conventional CPPs. Calculations predict ring currents and global aromaticity in the doubly charged system. The intriguing planar ring topology and unique electronic properties make planar π-extended CPPs promising quantum materials.
DOI: 10.1038/s41557-022-00968-3
Source: https://www.nature.com/articles/s41557-022-00968-3
