Effects of Connectivity Isomerization on Electron Transport Through Thiophene Heterocyclic Molecular Junction

作者：Hongyang Guo, Lin-Qi Pei, Zhuan‐Yun Cai, Sun Nan, Ju‐Fang Zheng, Yong Shao, Yahao Wang, De‐Yin Wu, Shan Jin, Xiao‐Shun Zhou · 发表于：Langmuir · 年份：2024 · DOI：10.1021/acs.langmuir.4c00678 · 被引用次数：13 · 研究领域：Molecular Junctions and Nanostructures、Organic Electronics and Photovoltaics、Graphene research and applications

Connectivity isomerization of the same aromatic molecular core with different substitution positions profoundly affects electron transport pathways and single-molecule conductance. Herein, we designed and synthesized all connectivity isomers of a thiophene ( TP ) aromatic ring substituted by two dihydrobenzo[b]thiophene ( BT ) groups with ethynyl spacers ( m, n -TP-BT, ( m, n = 2,3; 2,4; 2,5; 3,4)), to systematically probe how connectivity contributes to single-molecule conductance. Single-molecule conductance measurements using a scanning tunneling microscopy break junction (STM-BJ) technique show ∼12-fold change in conductance values, which follow an order of 10 −4.83 G 0 ( 2,4-TP-BT ) < 10 −4.78 G 0 ( 3,4-TP-BT ) < 10 −4.06 G 0 ( 2,3-TP-BT ) < 10 −3.75 G 0 ( 2,5-TP-BT ). Electronic structure analysis and theoretical simulations show that the connectivity isomerization significantly changes electron delocalization and HOMO−LUMO energy gaps. Moreover, the connectivity-dependent molecular structures lead to different quantum interference (QI) effects in electron transport, e.g., a strong destructive QI near E = E F leads the smallest conductance value for 2,4-TP-BT . This work proves a clear relationship between the connectivity isomerization and single-molecule conductance of thiophene heterocyclic molecular junctions for the future design of molecular devices.