Electrochemistry of Langmuir-Blodgett films incorporating both a viologen derivative and tetracyanoquinodimethane

A positively charged monolayer of a viologen derivative containing two long alkyl chains was prepared. Tetracyanoquinodimethane radical anions (TCNQ(.-)) were incorporated into the Langmuir-Blodgett film during the transference process as the counterions from a subphase containing an aqueous solution of LiTCNQ. Stable monolayers were transferred onto indium tin oxide electrodes and the electrochemical properties of the films were analyzed in terms of experimental variables including the nature of the counterions, the degree of order of the films, and the number of transferred layers. These well-ordered films show very reversible electrochemical processes for the viologen, quite negative redox potentials of the viologen moieties, a Gamma(c)/Gamma(a) ratio of 1, and no splitting of the first viologen reduction peak. The control of these properties is quite important in applications such as the catalytic reduction of a substrate. (C) 2002 The Electrochemical Society.