Dimerized Pi-Complexes in Self Assembled Monolayers Containing Viologens. AnOrigin of Unusual Waveshapes in the Voltammetry of Monolayers

摘要

Thiol derivatives of viologens self-assemble at gold and silver electrodes togive monolayers with relatively high surface coverages. Lateral interaction of the viologen redox groups in these monolayers is revealed by virtue of the formation of unique pi-complex diners (pi-mers) for the one-electron reduced form of viologens within these monolayers. The presence of these pi-mers is shown to give double-peaked voltammetric waves, and is unambiguously observed in the surface Raman (including SRRS, SERS and SERRS) spectra of these monolayers. The Raman bands due exclusively to the pi-mer as previously reported are assigned to the out-of-phase coupling nodes of the totally symmetric ring modes of the component cation radicals in the pi-mer. jg p.1.