2D mesoporous atomic monolayers of phenyleneethynylene oligomers on pyrolytic graphite surfaces analyzed by scanning tunneling microscopy
2D mesoporous atomic monolayers of phenyleneethynylene oligomers on pyrolytic graphite surfaces analyzed by scanning tunneling microscopy
复制标题
通过扫描隧道显微镜分析热解石墨表面上苯乙炔低聚物的二维介孔原子单层
DOI：
10.1016/j.apsusc.2020.145916
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发表时间：
2020
影响因子：
6.7
通讯作者：
S. Zappia
中科院分区：
文献类型：
--
作者：
Gleb Turlakov;E. Arias;I. Moggio;Joelis Rodríguez;G. Rodríguez;R. Ziolo;G. Scavia;S. Zappia
本文报道了四种线性和刚性π共轭对苯乙炔（PPE）低聚物的扫描隧道显微镜和小广角X射线散射和衍射。这四种化合物在中心PPE部分上具有两个十二烷氧基侧链，共轭长度不同（3和5个亚苯基亚乙炔基部分），并且是苄基、Bz 3 PEBz、Bz 5 PEBz或羧酸、Ac 3 PEAc、Ac 5 PEAc封端的。我们发现，在苯甲酸苄酯封端的低聚物中，通过苄基之间的π-π相互作用获得了分子的交错排列。相反，对于羧酸封端的低聚物，通过羧酸基团之间产生的氢键促进了相当线性的排列。一般来说，所有的分子形成采用正面排列的层状图案，其中共轭主链平放在HOPG表面上。薄层长度对应于低聚物共轭长度，而在薄层内，计算的距离对应于共轭主链之间的间距，平均值为2.06 nm，与XRD，SAXS和DFT/def-SVP发现的自组装与侧链烷基链交叉的低聚物一致。在其余的亚苯基亚乙炔基部分上缺乏更多的十二烷氧基侧链，导致在HOPG上形成介孔型自组装单分子膜。
We report on the scanning tunneling microscopy and small-wide angle X-ray scattering and diffraction of four linear and rigid π-conjugated p-phenyleneethynylene (PPE) oligomers. The four compounds possess two dodecanoxy side chains on the central PPE moiety, differ in conjugated length (3 and 5 phenyleneethynylene moieties) and are benzyl,Bz3PEBz,Bz5PEBz, or carboxylic acid,Ac3PEAc,Ac5PEAc, end-capped. We found that in the benzylbenzoate terminated oligomers, a staggered arrangement of molecules is obtained endorsed by the π-π interaction between the benzyls. In contrast, for the carboxylic acid terminated oligomers, a rather linear type arrangement is promoted by the hydrogen bond created between the carboxylic acid groups. In general, all of the molecules form a lamellar like pattern adopting face-on arrangements, where the conjugated backbones are flat-lying on the HOPG surface. The lamella length corresponds to the oligomer conjugation length, while within the lamellae, the calculated distances correspond to the spacing between conjugated backbones with an average value of 2.06 nm, consistent with that found by XRD, SAXS and DFT/def-SVP for the oligomers that self-assemble with the lateral alkyl chains interdigitated. The lack of more dodecanoxy side chains on the rest of the pheneyleneethynylene moieties gives rise to mesoporous type self-assembled monolayers on HOPG.