Synthesis and Size-Dependent Properties of [12], [16], and [24]Carbon Nanobelts

The synthesis and X-ray crystal structure of the first member of the carbon nanobelt family is reported. [12]Carbon nanobelt ([12]­CNB) was originally obtained from a nickel-mediated reductive coupling reaction of a dodecabrominated macrocyclic precursor, albeit only in 1% yield. The present article reports on the development of this synthetic strategy and its extension to the preparation of the [16] and [24]­CNB analogues. In particular, our extensive investigations on the final belt-forming, nickel-mediated reaction led to the development of a new ligand system that provides [12]­CNB in up to 7% yield, contributing to the commercialization of [12]­CNB. The belt structures of [12], [16], and [24]­CNB were characterized by NMR, UV–vis, and Raman spectroscopy as well as mass spectrometry and X-ray crystallography. The fluorescence of the CNBs in solution displayed a remarkable dependence on the ring size, ranging from a broad red emission ([12]­CNB) to a narrow-band blue emission ([24]­CNB), while both features are observed for [16]­CNB.

本研究报道了碳纳米带（Carbon nanobelt）家族首个成员的合成方法及其X射线晶体结构。[12]碳纳米带（[12]Carbon nanobelt，[12]CNB）最初通过十二溴代大环前驱体的镍介导还原偶联反应制得，但产率仅为1%。本研究详述了该合成策略的优化进程，并将其拓展至[16]CNB与[24]CNB类似物的制备。具体而言，我们针对最终成环的镍介导反应开展了系统性研究，开发出一种新型配体体系，可使[12]CNB的产率最高达到7%，为[12]CNB的商业化应用奠定了基础。我们通过核磁共振（NMR）、紫外-可见（UV–vis）光谱、拉曼（Raman）光谱，以及质谱与X射线晶体学对[12]CNB、[16]CNB及[24]CNB的环结构进行了表征。溶液态碳纳米带（CNBs）的荧光特性表现出对环尺寸的显著依赖性：[12]CNB呈现宽峰红色发射，[24]CNB则为窄带蓝色发射，而[16]CNB同时兼具这两种发射特征。