Tuning the reduction potential of quinones by controlling the effects of hydrogen bonding, protonation and proton-coupled electron transfer reactions

Abstract

An all-organic cell consisting of modified forms of vitamin E and vitamin K exhibited a large cell voltage, which was optimized via the use of diethyl malonate that served as a weak acid and hydrogen bond donor.

Non-covalent assembly of proton donors and p-benzoquinone anions for co-electrocatalytic reduction of dioxygen

“…The proposed instability is consistent with the observations of others. 13 With 1 and 1.37 M TFEOH under O 2 saturation conditions, the system exhibited comparable selectivity for H 2 O 2 compared to our previous report, 68(AE13)% (Fig. S41 and Table S3 †).…”

“…10h To the best of our knowledge, the use of hydrogen-bonded quinone anion adducts in an analogous role to their hydroquinone counterparts has only been applied to the study of quinone-based energy storage systems. 13 Given the profound interest in Mn complexes as electrocatalysts for O 2 reduction 5c,14 and the single report on the use of the BQ/H 2 Q redox couple in tandem with a molecular electrocatalyst to facilitate O 2 reduction, 8b we sought to carry out a study on the co-electrocatalytic competency of hydrogenbonded qunione anions using a Mn-based catalyst developed in our lab. 15 This molecular Mn complex, Mn( tbu dhbpy)Cl 1, where 6,6 0 -di (3,5- 2À , is a competent catalyst for the selective reduction of O 2 to H 2 O 2 (ca.…”

Synthesis of Amino Acid–Naphthoquinones and In Vitro Studies on Cervical and Breast Cell Lines

“…A full description of the electron-transfer mechanism of the naphthoquinones with amino acid substituents is beyond the scope of the present paper. However, it is assumed that the quinone dianion is possibly stabilized by an intramolecular hydrogen bond, since the dissociation of proton donor groups, i.e., carboxyl group, in DMSO is not facile, thus, cannot protonate the dianion [44,45,46,47]. In such a case, the second redox process merges with the first (Figure 2), owing to the stabilization of the dianion by a hydrogen bond, as reported elsewhere [35,46,48,49].…”

“…However, it is assumed that the quinone dianion is possibly stabilized by an intramolecular hydrogen bond, since the dissociation of proton donor groups, i.e., carboxyl group, in DMSO is not facile, thus, cannot protonate the dianion [44,45,46,47]. In such a case, the second redox process merges with the first (Figure 2), owing to the stabilization of the dianion by a hydrogen bond, as reported elsewhere [35,46,48,49]. For instance, the E 1/2 values computed for compounds 3b – e (~1.24 V) are located at the mid-point of the half-wave potential values determined for the semiquinone (Q − ) and the dianion (Q 2− ) redox reaction peaks of the parental 1,4-naphtoquinone compound studied at same experimental conditions, −0.9 V or −1.6 V, respectively (data not shown).…”

Rocking-Chair Proton Batteries with Conducting Redox Polymer Active Materials and Protic Ionic Liquid Electrolytes

“… 16 − 21 In addition, the versatile quinone redox chemistry is compatible with several different cycling cations, including alkali metal cations (e.g., Li + , Na + ), organic ammonium cations and protons, as well as with different solvents. 22 − 24 …”