Electrochemical behavior of substituted polycyclic aromatic quinones

Abstract

In an attempt to find molecules exhibiting different electrochemical properties in the presence and absence of light, a series of phenyl-and mesityl-substituted benzoquinones were synthesized. The half-wave potentials of these and other quiñones were measured in aqueous dioxane and anhydrous DMF and correlated with theoretical values calculated by the Hiickel method. The photoisomers of the phenyl-and mesitylsubstituted quiñones were obtained under irradiation but, due to facile hydrogen migration, rapidly rearranged into unreducible hydroxy hydrocarbons.In an attempt to find organic systems capable of storing light energy and restoring it at a later time, we are investigating the electrochemical behavior of electrochemically reducible photochromic compounds. Such systems should be capable under light irradiation to reach a metastable structure of higher energy and return only under controlled conditions to their ground state.If the structure of both forms differ sufficiently, then a shift in the reduction potential of a suitable group attached to the system1 might allow us to take advantage of the energy gained in the process of irradiation.In this series of communications, we are specifically interested in the following process found to occur readily with stilbene derivatives2 and report here the synthesis and polarographic study of a series of phenyl-and mesityl-substituted benzoquinones and other polyphenyl-substituted quiñones. Some of these compounds contain a stilbene fragment and hence are susceptible to cyclize reversibly under irradiation.3 This produces a change in conjugation and may lead to a shift in the reduction half-wave potentials.4 The role of the quinoidic group is to provide the required reversible oxidation-reduction center.

Photochemistry of Quinone-Bridged Amino Acids. Intramolecular Trapping of an Excited Charge-Transfer State

“…The second reduction wave was overlapped with the first reduction wave for AQAA, reflecting the involvement of the free acid functional groups in chemistry following two-electron reduction. The values for the one-electron half-wave potentials are consistent with those obtained for other substituted quinones for which the pattern is to move to more positve potentials with the addition of electron-withdrawing chlorine substituents and to more negative potentials on substitution with electron-donating amine groups. , …”

Synthesis, electrochemical and spectral properties of some ω-N-quinonyl amino acids

“…Ϫ ). The second wave is due to the reduction of the semiquinone anion-radical to hydroquinone dianion (Q 2Ϫ ) (Clambers, 1988), As expected (Klopman and Doddapaneni, 1974), the donor amino group increases the first reduction potential by over 300 mV with respect to the unsubstituted naphthoquinone (entries 2 and 3 vs. 1). However, the naphthoquinone derivative in entry 4, which also contains a chlorine atom as an electron-withdrawing group, exhibits two contradicting electronic effects.…”

Electrochemical Behavior of Aromatic Compounds on Nanoporous Gold Electrode

“…This is consistent with the literature as it is well known that a reversible transition between benzenediols to quinones typically includes a transfer of two electrons. 50,51 In addition, it is worth noting that the intensities of cathodic peaks corresponding to the reduction of gold oxides decreased for all solutions containing the aromatics. We tentatively attribute this to the less extent of gold oxidation due to competitive reactions of aromatics and/or to the inhibition of electron transfer required for gold oxidation/reduction by adsorbed products formed during the electrooxidation.…”