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 nondestructive attachment
to delicate nanomaterials like sp2 compounds. In this work,
we rationally synthesize molecular moieties with versatile functionalities.
A reactive anchor group allows us to attach them to carbon nanotubes
as defined charge-transfer agents while preserving the tubes’
π-conjugation. The charge-transfer agents were synthesized through
the stepwise nucleophilic substitution of either one (monosubstituted
series) or two (disubstituted series) chlorine 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 the methoxy group as an electron-transferring group helps us to
manipulate the electronic and optical properties of the molecular
probes and their charge transfer to the single-walled carbon nanotubes
(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 toward
the production of SWNTs with desired optical and electrical properties
by covalent π-preserving functionalization.