Tetrathiafulvalene-Tetracyanoquinodimethane Charge-Transfer Complexes Wired to Carbon Surfaces: Tuning of the Degree of Charge Transfer

Abstract

Charge-transfer complexes involving tetrathiafulvalene (TTF) and tetracyanoquinodimethane (TCNQ) derivatives are engineered in a 2D arrangement onto a carbon surface through the exposure of immobilized TTF units to TCNQ compounds. TTF molecules were immobilized as robust monolayers on carbon surfaces using the electrografting method followed by a click chemistry coupling. When the TTF monolayer is exposed to TCNQ, TCNQF2 (2,5-difluoro-TCNQ), and TCNQF4 (2,3,5,6-tetrafluoro-TCNQ), strong donor–acceptor complexes are formed onto the surface. A considerable decrease of the electrochemical response accompanies the formation of the charge-transfer complex. This observation is rationalized by the analysis of original crystal samples using an ultramicroelectrode cavity, confirming that charge-transfer complexes are electrochemically silent. A fine control of the degree of charge transfer with the judicious choice of different acceptors is evidenced through electrochemical and X-ray photoelectron spectroscopy (XP...