Substituent Effects in π-Stacking of Histidine on Functionalized-SWNT and Graphene.
Adsorptions of histidine on the functionalized (10,0) single-walled carbon nanotube (SWNT) and graphene were investigated using density function theory methods, M05-2x and DFT-D. The results show that the binding of the histidine ring to the functionalized SWNT is weaker than that to the pristine SWNT for both singlet and triplet complexes, regardless of the electron-donating (-OH, -NH2) or electron-withdrawing (-COOH) character and their attached sites. The present decreased binding is opposite to the well-known enhanced binding in the substituted benzene dimers. Since the atoms of the histidine are distant from the substituent atoms by over 6Å, there would be nodirectinteraction between histidine and the substituent as in the case of the substituted benzene systems. The decreased binding can be mainly driven by the aromaticity of the functionalized SWNT. The nucleus-independent chemical shift (NICS) index analysis for the functionalized SWNTs in deed shows that local aromaticity of SWNT is decreased because of the electron redistribution induced by functional groups, and theπ-πstacking between the histidine ring andfunctionalized-SWNT is therefore decreased as compared to the pristine SWNT. However, the above trend does not remain for the binding between the histidine and graphene. The binding of the histidine to the functionalized graphene with -OH and -NH2is just slightly weaker than that to the pristine graphene, while its binding to COOH-SWNT becomes a little bit stronger.
School of Chemistry and Pharmaceutical Engineering, Qilu University of Technology, Jinan, Shandong 250353, China ; Department of Natural Science, Albany State University, Albany, GA 31705, USA.
Ge
G
Tian
Department of Natural Science, Albany State University, Albany, GA 31705, USA ; Department of Chemistry, Gannan Normal University, GanZhou, JiangXi 341000, China.
Huifang
H
Li
School of Chemistry and Pharmaceutical Engineering, Qilu University of Technology, Jinan, Shandong 250353, China.
Wanyong
W
Ma
Department of Natural Science, Albany State University, Albany, GA 31705, USA.
Yixuan
Y
Wang
DFT-D; NICS; functionalized-SWNTs; substituent effects; π-π stacking interactions