Electrochemical Behavior of the Naphtoquinone Anchored onto a Gold Electrode through the Self-Assembled Monolayers of Aminoalkanethiol

Abstract

2,3-Dichloro-1,4-naphtoquinone (NQ) was anchored to a gold electrode surface through the self-assembled monolayers of aminoalkanethiols (AAT, HS(CH2)nNH2: n = 2, 5, and 8). The effect of the alkyl chain length of the AAT monolayer, which also acts as the spacer between the NQ molecule and the gold electrode surface, on the redox behavior of the immobilized NQ has been studied by using a voltammetric technique. The surface coverage of the anchored NQ was estimated to be 3.8 × 10−10 mol cm−2 in the case that 2-aminoethanethiol (HS(CH2)2NH2) was used as the monolayer constituent. The electron-transfer rate constant, ket, associated with the redox process of anchored NQ decreased from 9.7 s−1 at n = 2 to 0.78 s−1 at n = 8, with increasing the chain length of the AAT monolayer, though the redox potential of NQ was scarcely affected by the chain length. The tunneling barrier coefficient, β, of the electron transfer was estimated to be 0.36 Å−1, from the observed linear relationship between the ket value and the monolayer chain length.

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

“…In the biological process, quinone pigments play a key role in the electron and proton transfers [1]. Recently, electron transfer in a self-assembled monolayer (SAM) of quinone derivative on a gold electrode has been reported to clarify the electron transfer on the surface of the electrode [2][3][4]. The SAMs on a gold electrode by using alkylthiols and dialkyldisulfides of various alkyl chain lengths were very useful for controlling the distance between the quinone moiety and the electrode surface.…”

“…The SAMs on a gold electrode by using alkylthiols and dialkyldisulfides of various alkyl chain lengths were very useful for controlling the distance between the quinone moiety and the electrode surface. It is interesting to note that the effects of the quinone structure and the distance on the electron-transfer rate between the quinone and electrode can be easily examined by using SAM of quinone derivative on a gold electrode [2][3][4].…”

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].…”

Surface Diluent Effect on the Heterogeneous Electron-transfer Kinetics of PQQ Self-assembled Monolayers

“…They include ruthenium or osmium complexes, 2,3 ferrocene, 4,5 viologen, 6 azobenzene, 7,8 and various quinone systems. [9][10][11][12][13][14] Quinones are important as they play an important role in biological systems. 15 Focus has mostly been made on the evaluation of the tunneling barrier constant (β) and the dependency of ET rate constant on the structure of bridges connecting an electrode and an electroactive center.…”

“…1.0 Å -1 per CH2 unit, different β values have been reported for different quinines. 9,16 The heterogeneous ET rate constant is greatly affected by the nature of bridging molecules. Conjugated bridges give higher ET rate constant compared to unconjugated systems.…”