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- Title
Organic Diodes Based on Redox-Polymer Bilayer-Film-Modified Electrodes.
- Authors
Zhao, Wenyuan; Marfurt, Judith; Walder, Lorenz
- Abstract
The synthesis of four electropolymerizable 2,2′-bipyridinium salts with tuned reduction potential ( E1∘) is described ( N, N′-ethylene-4-methyl-4′-vinyl-2,2′-bipyridinium dibromide ( 4; E1∘ -0.48 V), 4-methyl- N, N′-(trimethylene)-4′-vinyl-2,2′-bipyridinium dibromide ( 5; E1∘ −0.66 V), N,N′-ethylene-4-methyl-4′-[2-(1 H-pyrrol-1-yl)ethyl]-2, 2′-bipyridinium bis(hexafluorophosphate) ( 6b; E1∘ −0.46 V), and 4-methyl-4′-[2-(1 H-pyrrol-1-yl)ethyl]- N, N′-(trimethylene)-2,2′-bipyridinium bis(hexafluorophosphate) ( 7b; E1∘ −0.66 V)). E1∘-Tuning is based on the torsional angle C(3)-C(2)-C(2′)-C(3′), imposed by the N,N′-ethylene and N,N′-(trimethylene) bridge. The vinylic compounds 4 and 5 undergo cathodic, the pyrrole derivatives 6b and 7b anodic electropolymerization on glassy carbon electrodes from MeCN solutions, yielding thin, surface-confined films with surface concentrations of redox-active material in the range 5 · 10−9 −8 mol/cm2, depending on experimental conditions. The modified electrodes exhibit reversible 'diquat' electrochemistry in pure solvent/electrolyte. Copolymerization of 6b or 7b with pyrrole yields most stable electrodes. Bi ayer-film-modified electrodes were prepared by sequential electropolymerization of the monomers. The assembly electrode/poly- 6b/poly- 7b behaves as a switch, it transforms - as a Schmitt trigger - an analog input signal (the electrode potential) into a digital output signal (redox state of the outer polymer film). Forward-(electrode/poly- 7b/poly- 6b) and reverse-biased assemblies (electrode/poly- 6b/poly- 7b) were coupled to the electrochemical reduction of redox-active solution species, e.g. N- (cyanomethyl)- N′-methyl-4,4′-bipyridinium bis(hexafluorophosphate) ( 8). Zener-diode-like behavior was observed. Aspects of redox-polymer multilayer-film assemblies, sandwiched between two electronic conductors, are discussed in terms of molecular electronic devices.
- Publication
Helvetica Chimica Acta, 1994, Vol 77, Issue 1, p351
- ISSN
0018-019X
- Publication type
Academic Journal
- DOI
10.1002/hlca.19940770134