Synthesis of 1,4-hydroquinone-terminated alkanethiol and self-assembly on gold as characterized by interfacial electrochemistry, electrocatalysis application and ab initio calculation based on comparison with catechol-presenting analogue

Synthesis and self-assembly of a mercaptoundecaneamide derivative having a terminus of 1,4-hydroquinone (QT) are described. Electrochemical measurements on the QT-modified Au electrode revealed that the alkanethiol compound undergoes self-assembly to exhibit specific electrochemical activity originates from the reversible quinone/hydroquinone redox reaction at the terminus. We have achieved to obtain the electrochemical active surface coverage (0.11 nmol cm−2), formal potential (+246 mV, pH 3, Ag/AgCl) that changes pH-dependently (58 mV per pH) and also a set of the electron transfer reaction parameters, all of which were consistent with those of the previously reported structural isomer, catechol-terminated mercaptoundecaneamide (CT). Contrastingly, we found that these alkanethiol monolayers give marked contrast in an elecrocatalysis application: the CT-monolayer electrodes showed electrocatalytic capability in oxidation of NADH solution species while the QT-monolayer electrodes did not at all. By comparing some results of theoretical approach, we have attributed the surface selectivity to the spatiality of particular molecular orbital in the catalysis molecule. This observation should be important as an example of spatiality–reactivity relationships in a molecular design of chemically modified electrode.