Effect of Single-Walled Carbon Nanotube Association upon 1H NMR Spectra of Amines

Abstract

In order to quantify and study the complexation of small organic amine molecules with SWCNTs, the effect of SWCNT association upon their proton NMR spectra was studied. Results reveal that (1) a greater magnitude of chemical shift change for α protons to the amino group upon SWCNT association suggests close proximity of the amine nitrogen to SWCNTs except for the pyridines, (2) tertiary amines associate strongly with SWCNTs due to the inductive effect outweighing the steric effect of their alkyl parts, (3) in secondary amines, the steric effect overpowers the inductive effect resulting in their weaker interaction than tertiary amines with SWCNTs, (4) introduction of an alkyl substituent at the α position in primary amines results in more effective SWCNT association than at the amino nitrogen in secondary amines, (5) aromatic amines associate more strongly than aliphatic ones due to availability of more points of association, and (6) pyridines seem to interact via their π-electron cloud.