Mixed monolayers formed by the self-assembly on gold of thiol-functionalized anthraquinones and 1-alkanethiols

Abstract

The self-assembly and electrochemical properties of a series of thiol-functionalized anthraquinone derivatives were studied on gold by cyclic voltammetry. The compounds were l,8-bis(l,7-dithia-4-oxaheptyl)anthracene-9,10-dione (1), l,8-bis(4,7-dioxa-l,10-dithiadecyl)anthracene-9,10-dione (2), and l-(4,7-dioxal,10-dithiadecyl)anthracene-9,10-dione (3). Compounds 1-3 formed self-assembled monolayers on gold with surface coverages of 2.7 X Kb10, 2.5 X 10~10, and 2.9 x 10"10 mol/cm1 2, respectively. All monolayers showed voltammetric responses in 0.1 KOH that corresponded to the two-electron reduction of the anthraquinone subunit. However, the voltammetric response was not reversible, exhibiting large peakto-peak potential splittings (60-80 mV at a scan rate of 0.1 V/s) and other distortions. The voltammetric reversibility increased substantially in mixed monolayers prepared by the competitive self-assembly of one of the anthraquinone derivatives and a 1-alkanethiol (Ci0 to C18). Interestingly, the anthraquinone derivatives competed quite effectively with alkanethiols for adsorption sites on the gold surface. Compound 2 was found to be optimum in this regard because it has two thiol-terminated chains that may serve as anchoring points to the gold surface.

Electrochemical and structural properties of self-assembled monolayers of 2-methyl-3-(ω-mercaptoalkyl)-1,4-naphthoquinones on gold

“…The minimization of lateral interactions between the terminal headgroups by forming mixed monolayers with simple 1-alkanethiols has been demonstrated previously [19]. Mixed SAMs of thiol-functionalized antraquinones and 1-alkanethiols showed the improved reversibility of redox process [23]. Studies of the mixed hydroquinone-terminated SAMs revealed the crucial influence of the chain length of diluent alkanethiol on the hydroquinone head-group electrochemical response [24].…”

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.…”