Centre for Industrial Collaboration, School of Chemistry, University of Leeds, LS2 9JT, UK.
Nanoscale. 2018 Apr 26;10(16):7639-7648. doi: 10.1039/c8nr01216d.
Carbon nanomaterials such as polyaromatic hydrocarbons (PAHs), graphene, fullerenes and nanotubes are on the frontline of materials research due to their excellent physical properties, which in recent years, have started to compete with conventional inorganic materials in charge transfer based applications. Recently, a variety of new structures such as single-walled carbon nanobelts (SWCNBs) have been conceived, however, to date only one 'all-phenyl' example has been synthesised, due to problems with their stability and the challenging synthetic methodologies required. This study introduces a new class of phenacene-based SWCNBs and their chalcogenide derivatives, forming the new sub-class of single-walled heterocyclic carbon nanobelts (SWHNBs) which are expected to be both more stable and easier to synthesise than the all carbon analogues. Subsequent theoretical examination of the structure-property relationships found that unlike the small-molecule acene homologues (tetracene, pentacene etc.) which become more reactive with addition of oxygen, an increase in the molecular size of the SWCNBs actually stabilises the HOMO energy level, in correlation with the increasingly negative nuclear independent chemical shift (NICS) calculations of their cylindrical aromaticities. The FMO energies of the phenacene SWCNBs are similar to that of the nanobelt reported by Itami and co-workers, but those of the SWHNBs are deeper and thus more stable. The sulfur derivative of one SWHNB was found to give hole-charge transfer mobilities as high as 1.12 cm2 V-1 s-1, which is three orders of magnitude larger than the corresponding unsubstituted SWCNB (3 × 10-3 cm2 V-1 s-1). These findings suggest the candidates are air-stable and potentially high-performing organic semiconductors for organic thin film transistor (OTFT) devices, while the structure-property relationships uncovered here will aid the design and synthesis of future three-dimensional organic nanomaterials.
碳纳米材料，如多环芳烃（PAHs）、石墨烯、富勒烯和纳米管，由于其优异的物理特性，成为材料研究的前沿，近年来，它们在基于电荷转移的应用中开始与传统无机材料竞争。最近，各种新型结构，如单壁碳纳米带（SWCNBs），已经被构想出来，然而，迄今为止，由于它们的稳定性问题和所需的具有挑战性的合成方法，仅合成了一种“全苯基”的例子。本研究介绍了一类新型的菲基 SWCNBs 及其硫属元素衍生物，形成了新的单壁杂环碳纳米带（SWHNBs）亚类，预计比全碳类似物更稳定，更容易合成。随后对结构-性质关系的理论研究发现，与小分子并五苯同系物（苝、芘等）不同，随着氧的加入，其反应性增强，SWCNBs 的分子尺寸增加实际上会稳定 HOMO 能级，与它们圆柱芳香性的核独立化学位移（NICS）计算值的负性增加相关。菲基 SWCNBs 的 FMO 能量与 Itami 及其同事报道的纳米带相似，但 SWHNBs 的能量更深，因此更稳定。一个 SWHNB 的硫代衍生物被发现具有高达 1.12 cm2 V-1 s-1 的空穴电荷转移迁移率，比相应的未取代 SWCNB（3 × 10-3 cm2 V-1 s-1）高三个数量级。这些发现表明，这些候选物是空气稳定的，并且可能是用于有机薄膜晶体管（OTFT）器件的高性能有机半导体，而此处揭示的结构-性质关系将有助于未来三维有机纳米材料的设计和合成。
