On the Adsorption of Extended Viologens at the Electrode|Electrolyte Interface

Abstract

Extended viologens represent a group of organic molecules intended to be used as molecular wires in molecular electronic devices. Adsorption properties of a novel series of extended viologen molecules were studied at the mercury electrode|electrolyte interface. These compounds form compact monolayers around the potential of zero charge with a constant differential capacitance value of 2.5 ± 0.2 μF cm(-2) independent of temperature, length of the molecule, and its bulk concentration. At more negative potentials their reduction in the adsorbed state takes place. We showed that the adsorption process is diffusion controlled and time needed to fully cover the electrode surface is independent of the electrode potential. A modified Koryta equation was employed for the calculation of the surface concentration of the adsorbates leading to the value of 5.3 × 10(-11) mol cm(-2) for the shortest wire and to 1.6 × 10(-11) mol cm(-2) for the longest one. Based on the space filling model and the differential capacitance value in the compact film region, it was postulated that these molecules lay flat on the electrode surface.

Direct Electricity Generation from Dissolved Cellulosic Biomass in an Alkaline Fuel Cell

“…The best‐known viologen is methyl viologen (MV), which is one of the world's most widely used herbicides. MV is also a good electron mediator that has great possibilities to be used with an electrode system in which the electrode system provides electrons for reducing MV species . An alkaline fuel cell using MV as the catalyst and nickel foam as the anode material, which is capable of harnessing electrical power from carbohydrate at low temperature has been reported , .…”

Adsorption of Expanded Pyridinium Molecules at the Electrified Interface and Its Effect on the Electron-Transfer Process

“…Phase-sensitive ac (alternating current) voltammetry and time-resolved differential capacitance measurements were obtained at frequency 160 Hz and ac signal amplitude of 5 mV. Direct current (dc) potential of the electrode was incremented by 10 mV toward more negative values every 3 s. Further experimental details are described elsewhere . All experiments were performed at 25 °C.…”

“…Advancement of molecular electronics requires proper knowledge of the adsorption properties of organic molecules on conducting surfaces as a prerequisite for the formation of molecular electronic junctions of desired functionalities. − In the so-called break junction experiment, two electrodes are being brought in (approach curves) and out (withdrawal curves) of contact in a solution of respective molecules. By applying a small voltage difference between the electrodes, one can measure an electric current and construct a current–distance curve characterizing the junction.…”

Electron dopable molecular wires based on the extended viologens

“…The evaluation method of the diffusion coefficients of the compounds was described previously. 7 The number of electrons was confirmed independently by the double step chronoamperometric measurements in the OTTLE cell with the dimethyl viologen redox system used as a standard. 48 The shortest molecule 1 shows four one-electron reduction steps (curve 1 in Fig.…”

“…Extended viologens are molecules containing two pyridinium moieties separated by a suitable spacer such as alkyl chain, ethylene, butadienylene, phenylene or heteroaromatic ring. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Molecules with several repeating extended viologen units are often designated as molecular wires, since one of their dimensions (length) greatly exceeds the diameter of the molecule. Extended viologen molecules alike viologens are easily dopable with electrons 2,3,[18][19][20][21][22] and this property can be utilized in many applications from new electrochromic materials to molecule-based electronics.…”