Synthesis of Multifunctional Charge Transfer Agents: Towards Single Walled Carbon Nanotubes with Defined Covalent Functionality and Preserved {\pi} System

TL;DR

This study develops covalent charge transfer agents with tunable electronic properties for attaching to single-walled carbon nanotubes, aiming to modify their optical and electrical characteristics while preserving their π system.

Contribution

It introduces a systematic synthesis of multifunctional charge transfer agents that can attach to SWNTs without disrupting their π conjugation, enabling tailored nanomaterial properties.

Findings

Charge transfer agents' optoelectronic properties are influenced by aniline segments.

The triazine moiety enables non-destructive attachment to SWNTs.

Systematic manipulation of optical properties through methoxy group variation.

Abstract

The attachment of well-defined charge transfer agents to the surface of nanomaterials is an efficient strategy to control their charge density and also to tune their optical, electrical, and physicochemical properties. Particularly interesting are charge transfer agents that either donate or withdraw electrons depending on the arrangements of their building units and that promise a non-destructive attachment to delicate nanomaterials like sp$^2$ compounds. In this work, we rationally synthesize molecular moieties with versatile functionalities. A reactive anchor group allows to attach them to carbon nanotubes as defined charge transfer agents while preserving the tube $\pi$-conjugation. The charge transfer agents were synthesized through the stepwise nucleophilic substitution of either one (monosubstituted series) or two chlorine (disubstituted series) atoms of cyanuric chloride by aniline derivatives containing one, two or three methoxy groups in the para and meta positions. Variation in the number and position of methoxy as an electron transferring group help us to manipulate the electronic and optical properties of the molecular probes and their charge transfer to the SWNTs systematically. The correlation between the optical properties of these molecular probes and their functionality was investigated by experiments and quantum chemical calculations. While the optoelectronic properties of the conjugated charge transfer agents were dominated by the aniline segments, the triazine warrants the ability to nondestructively attach to the surface of SWNTs. This study is one step ahead towards the production of SWNTs with desired optical and electrical properties by covalent $\pi$-preserving functionalization.