Department of Chemistry, Optoelectronic Nano Materials and Devices Institute, Shanghai Normal University , Shanghai, China.
J Am Chem Soc. 2014 Jun 4;136(22):8122-30. doi: 10.1021/ja503533y. Epub 2014 May 20.
We describe the design and synthesis of a new graphene ribbon architecture that consists of perylenediimide (PDI) subunits fused together by ethylene bridges. We created a prototype series of oligomers consisting of the dimer, trimer, and tetramer. The steric congestion at the fusion point between the PDI units creates helical junctions, and longer oligomers form helical ribbons. Thin films of these oligomers form the active layer in n-type field effect transistors. UV-vis spectroscopy reveals the emergence of an intense long-wavelength transition in the tetramer. From DFT calculations, we find that the HOMO-2 to LUMO transition is isoenergetic with the HOMO to LUMO transition in the tetramer. We probe these transitions directly using femtosecond transient absorption spectroscopy. The HOMO-2 to LUMO transition electronically connects the PDI subunits with the ethylene bridges, and its energy depends on the length of the oligomer.
我们描述了一种新的石墨烯带结构的设计和合成，该结构由通过亚乙基桥键合在一起的苝二酰亚胺（PDI）亚基组成。我们合成了一系列由二聚体、三聚体和四聚体组成的寡聚物原型。PDI 单元之间的融合点的空间位阻导致了螺旋结的形成，而较长的寡聚物则形成了螺旋带。这些寡聚物的薄膜在 n 型场效应晶体管中形成了活性层。紫外可见光谱显示四聚体中出现了一个强烈的长波长跃迁。通过 DFT 计算，我们发现 HOMO-2 到 LUMO 的跃迁与四聚体中 HOMO 到 LUMO 的跃迁等能。我们使用飞秒瞬态吸收光谱直接探测这些跃迁。HOMO-2 到 LUMO 的跃迁在电子上将 PDI 亚基与亚乙基桥连接起来，其能量取决于寡聚物的长度。
