Amino acids are basic units to construct a protein with the assistance of various interactions.During this building process,steric hindrance derived from amino acid side groups or side chains is a factor that could not be ignored.In this contribution,adsorption behaviors of C-terminal amino acid derivatives with amino acid residues fused in 3,4,9,10-perylenetetracarboxylic dianhydride were investigated by scan-ning tunneling microscopy(STM)and density functional theory(DFT)calculations at various liquid/solid interfaces.STM results at 1-phenyloctane/HOPG interface show that N,N'-3,4,9,10-perylenedicarboximide(GP)and N,N'-methyl-3,4,9,10-perylenedicarboximide(AP)formed linear and herringbone structures,re-spectively.The driving force could be attributed to different H-bonding sites induced by steric hindrance at side groups.N,N'-Benzyl-3,4,9,10-perylenedicarboximide(PP)generates both linear and herringbone structures because steric hindrance changes the H-bonding sites between PP molecules,whereas N,N'-isopropyl-3,4,9,10-perylenedicarboximide(LP)failed to be imaged because of strong steric hindrance coming from larger side group.To further investigate the impact of steric hindrance,we utilized octanoic acid(OA)as solvent to capture the adsorption details of LP and PP.We found that OA molecules drag PP and LP molecules in a different direction to generate linear structure,impeding the molecular rotation.The structure-solvent relationship shows that the steric hindrance is brought by the large side group,which makes it easier to recognize OA molecules at the interface.These results demonstrate that steric effect plays a significant role in altering interaction sites of the compounds during the adsorption process at the liquid/solid interface.

Yunzhi Xie;Chunhua Liu;Linxiu Cheng;Yulan Fan;Huifang Li;Wei Liu;Lei Zhu;Xun Li;Ke Deng;Qingdao Zeng;Shoufa Han

State Key Laboratory for Physical Chemistry of Solid Surfaces,Department of Chemical Biology,College of Chemistry and Chemical Engineering,The Key Laboratory for Chemical Biology of Fujian Province,The MOE Key Laboratory of Spectrochemical Analysis&Instrumentation,and Innovation Center for Cell Signaling Network,Xiamen University,Xiamen 361005,China;Jiangxi Key Laboratory of Organo-Pharmaceutical Chemistry,Chemistry and Chemical Engineering College,Gannan Normal University,Ganzhou 341000,China;Jiangxi Provincial Key Laboratory of Low-Carbon Solid Waste Recycling,School of Geography and Environmental Engineering,Gannan Normal University,Ganzhou 341000,China;CAS Key Laboratory of Standardization and Measurement for Nanotechnology,CAS Center for Excellence in Nanoscience,National Center for Nanoscience and Technology(NCNST),Beijing 100190,China

中国化学快报（英文版）

[1]Yunzhi Xie;Chunhua Liu;Linxiu Cheng;Yulan Fan;Huifang Li;Wei Liu;Lei Zhu;Xun Li;Ke Deng;Qingdao Zeng;Shoufa Han-.Single molecular insight into steric effect on C-terminal amino acids with various hydrogen bonding sites)[J].中国化学快报（英文版）,2022(10):4649-4654

perylenetetracarboxylic,phenyloctane,perylenedicarboximide,Benzyl,octanoic

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