Covalent functionalization of single-walled carbon nanotubes by Bingel reaction for building charge-transfer complexes

Abstract

Functionalization of nanotubes with donor and acceptor partners by the Bingel reaction leads to formation of charge-transfer dyads, which can operate in organic photovoltaic devices. In this work, we theoretically examine the mechanism of the Bingel reaction for (6,5)-chiral, (5,5)-armchair, and (9,0)-zig-zag single-walled carbon nanotubes (SWCNTs), and demonstrate that the reaction is regioselective and takes place at the perpendicular position of (6,5)- and (5,5)-SWCNTs, and oblique position of (9,0)-SWCNT. Further, we design computationally the donor-acceptor complexes based on (6,5)-SWCNT coupled with partners of different electronic nature. Analysis of their excited states reveals that efficient photoinduced charge transfer can be achieved in the complexes with exTTF, ZnTPP, and TCAQ. The solvent can significantly affect the population of the charge separated states. Our calculations show that electron transfer (ET) occurs in normal Marcus regime on sub-nanosecond time scale in the complexes with exTTF and ZnTPP, and in inverted Marcus regime on picosecond time scale in the case of TCAQ derivative. The ET rate is found to be not very sensitive to the degree of functionalization of the nanotube