Electron transfer in self-assembled monolayers of N-methyl-N'-carboxyalkyl-4,4'-bipyridinium linked to gold electrodes

Abstract

Electron transfer processes in monolayer assemblies formed by covalent linkage of JV-methyl-JV'carboxyalkyl-4,4'-bipyridinium (1) to cystamine, chemisorbed onto gold electrodes, are examined. The resulting monolayer exhibits nonordered structure being reflected by a similar rate constant to the bipyridinium redox sites, that is independent of the bridging alkyl chain length, ket = 550 a-1. The nonordered structure is also confirmed by the low electron transfer coefficients aa and ac, corresponding to 0.25 ± 0.05 and 0.3 ± 0.05, respectively. By treatment of the nonordered monolayer assembly with 1-hexadecanethiol, CieSH, a more densely packed organized monolyer is formed, where the alkyl-substituted bipyridinium sites are stretched in the monolayer configuration. In these assemblies the electron transfer rate constants to the bipyridinium sites depend on the alkyl chain length bridging the redox site to the electrode. The electron transfer rate constants follow Marcus theory and the electron tunneling coefficient corresponds to ß = 0.006 A-1.

Electron transport in bipyridinium films

“…In both instances, the sulfur‐containing functional group ensures the adsorption of these compounds on the surface of a gold electrode and the bipyridinium dication imposes electroactive character on the resulting films. A different approach to similar monolayers is based, instead, on the use of bipyridinium compounds with pendant carboxylic acids 42. For example, a gold electrode can be coated with a monolayer of cystamine.…”

Electron transfer of quinone self-assembled monolayers on a gold electrode

“…The electron transfer for SAM of various compounds with redox moieties on a gold electrode has been studied so that the rate constant is found to increase with decreasing the distance between the redox group and the electrode according to the Marcus theory [2][3][4][5][6][7][8][9][10][11][12][13].…”

Phospholipid-linked quinones-mediated electron transfer on an electrode modified with lipid bilayers

“…The phospholipid-linked manganese porphyrins exhibited an enhanced electron transfer activity, depending upon the length of the spacer methylene group (C n ) and also the structure of manganese porphyrins. Alternatively, a large number of chemists have identified that electroactive species such as porphyrins, myoglobin, flavins, viologens, ferrocenes and quinones can be immobilized on electrode surfaces [23][24][25][26][27][28][29]. However, there has been little study of electron transfer between quinones or porphyrins complexes on an electrode modified with lipid bilayers 0927 [4,30,31].…”