CarbonNanotubesConjugatedwithTriazole-BasedTetrathiafulvalene-TypeReceptorsfor C60Recognition

Abstract

Fullerene receptors prepared by a twofold CuI -catalyzed azide-alkyne cycloaddition (CuAAC) reaction with -extended tetrathiafulvalene (exTTF) have been covalently linked to singlewalled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). The nanoconjugates obtained were characterized by several analytical, spectroscopic and microscopic techniques (TEM, FTIR, Raman, TGA and XPS), and evaluated as C60 receptors by UV-Vis spectroscopy. The complexation between the exTTF-triazole receptor in the free state and C60 was also studied by UV-Vis and 1 H NMR titrations, and compared with analogous triazole-based tweezer-type receptors containing the electron-acceptor 11,11,12,12-tetracyano-9,10-anthraquinodimethane (TCAQ) and benzene rings instead of exTTF motifs, providing in all cases very similar values for the association constant (log Ka  3.0‒3.1). Theoretical density functional theory (DFT) calculations demonstrated that the enhanced interaction between the host and the guest upon increasing the size of the -conjugated arms of the tweezer is compensated by an increase in the energy penalty needed to distort the geometry of the host to wrap C60.