2-Methyl-1,4-naphthoquinones containing 3-[N-(ω-mercaptoalkyl)alkanamide] chains: synthesis, self-assembling, and electrochemical properties

Effect of hydrogen-interactions on electrochemical behavior of bithiophene self-assembled monolayers containing amide moieties

“…For all compounds, surface coverages (C) calculated from the charge integration recorded during the first oxidation process are similar after 15 s immersion (2 Â 10 À10 -3 Â 10 À10 mol cm À2 ). These results, which demonstrate that the formation of hydrogen bond inside the monolayer does not have a significant impact on the surface coverage, are in accordance with those obtained by Kazemekaite et al [1]. In order to differentiate the steric influence from the attractive hydrogen bonding effect of the amide groups, they made a comparison with monolayers containing ester groups.…”

“…In contrast, CV recorded on the 2-ht SAM exhibits a positive shift of the formal potential for both redox systems (DE 1 $ 50 mV for the first wave and DE 2 $ 30 mV for the second wave). This fact is in accordance with the proximity of the carbonyl electrowithdrawing functionality to the electroactive site and is in agreement with the results reported by Kazemekaite et al [1] and by Sabapathy et al [18] who observed a similar shift of the formal potential when the carbonyl function is close to the electroactive ferrocenyl moiety.…”

“…In fact, the presence of strong intermolecular interactions between neighboring molecules can induce changes in the electronic transfer kinetics through the adsorbate chains [1][2][3][4], the formal redox potential of immobilized electroactive groups [1], the packing density [1,5,6] or the stability of the SAM [7][8][9][10][11][12]. If data reported in the literature confirm that interactions between immobilized species influence the physic and chemical behaviors of the SAM, contradictory conclusions are drawn concerning the variations of the properties enounced with the position of the amide moieties on the backbone.…”

Electrochemical investigations of dissolved and surface immobilised 2-amino-1,4-naphthoquinones in aqueous solutions

“…Taking n = 2 and a = 0.5, which is reasonable in view of the symmetry of the Laviron plot (see below), a value of k s = 2.0 Â 10 2 s À1 is calculated. This value is higher, by at least one order of magnitude, than those reported for other self-assembled monolayers of naphthoquinones [18,20,23,24,26,27]. A direct comparison is however difficult because the electron transfer rate is influenced by many parameters including the quinone structure, the pH, the chemical structure of the bridge between the electrode and the redox group, and the fabrication of the self-assembled monolayer.…”

“…Other 2-amino-1,4-naphthoquinones, dissolved in solution, are used as reference systems to help interpret the voltammetric response of the immobilised naphthoquinone (NQ). A few reports have already been devoted to the synthesis, self-assembly and electrochemical characterisation of NQ derivatives immobilised on gold electrodes [18,[20][21][22][23][24][25][26][27]. Naphthoquinone occurs naturally as the core structure of the vitamin K family, involved in various biological processes.…”