Fast dimerisation of the triparaquat radical dication

Abstract

The one-electron reduction of 2,4,6-tris(N-methylpyridinium-4-yl)pyridine trication, triparaquat, TPQ3`, synthesized in the form of the perchlorate salt, was studied by cyclic voltammetry on a platinum disc electrode. It was found that the reduction peak is centered at [880 mV (vs. SCE) at 500 mV s~1 scanning rate. The subsequent oxidation takes place at ]75 mV, indicating an irreversible process, but no changes in the solution content were found after the oxidation. The blue colored reduction product reacts anomalistically slowly with oxygen with a second-order rate constant of (0.65 ^0.01) mol~1 dm3 s~1. EPR experiments showed that the reduction product in ethanol solution does not possess an unpaired electron. A low temperature gamma radiolysis experiment revealed that the spectral peak maximum of the reduction product of TPQ3`solubilized in PVA Ðlm is shifted D200 nm with respect to that obtained in aqueous solution at room temperature. Pulse radiolysis experiments proved that this seemingly inconsistent set of data was a consequence of the very fast dimerisation process mol~1 dm3 s~1). Cyclic voltammetry 2TPQ2`~¢ (TPQ) 2 4`(k dim \ 1.4 ] 109 experiments on a mercury electrode revealed that the second reduction step corresponds to the dimer reduction. The third and fourth reduction steps were irreversible and initiated further chemical reactions of triparaquat, which was consistent with the data obtained by the prolonged steady state gamma radiolysis. Fig. 1 Structural formulae of triparaquat, TPQ3`, methyl viologen, MV2`and 1-ethylpyridinium, EP`.

Face-Dependent Electron Transfer in CdSe Nanoplatelet–Methyl Viologen Complexes

“…Therefore, the fast relaxation at the heavy-hole band of the CdSe NPL−MV 2+ complexes was due to electron transfer from the band-edge state of the CdSe NPLs to MV 2+ . Furthermore, as shown in Figure S8, an absorption band centered at 620 nm corresponding to the methyl viologen cation radical (MV + radical) 43 was observed in the transient absorption spectra, further supporting that the electron is transferred from the CdSe NPLs to MV 2+ . As the formation of the MV + radical originated from the electron transfer from the CdSe NPLs to MV 2+ , the rise components of the MV + radical However, the amplitudes of two rise and decay components does not match well with each other.…”

Electrostatic interactions between viologens and a sulfated β-cyclodextrin; formation of insoluble aggregates with benzyl viologens

“…5, where the first oxidation peak may arise from the oxidation of insoluble V 0 , soluble V 0 and an insoluble dimer:sβ-CD. The structure of the viologen dimer is not fully elucidated, however there is a general acceptance that it exists in solution in a face-to-face orientation arising from the overlapping π system of the two viologen molecules [33].…”