Electrochemical behavior of 1,2-dihydroxyanthraquinone dianion in aprotic solvents-DMSO and DMF: understanding the hydrogen bonding phenomena and protonation effect in biochemical systems

Abstract

In this work, we report, the electrochemical properties of 1,2-dihydroxyanthraquinone through cyclic voltammetry (CV) and square wave voltammetry (SWV) in two aprotic solvents-DMSO and DMF. It is investigated that 1,2-dihydroxyanthraquinone undergoes two single-electron reduction processes. The first electron transfer process corresponds to formation of anion radical while the second electron transfer corresponds to dianion of 1,2-dihydroxyanthraquinone. Concentration effect and scan rate effect on CV of 1,2-dihydroxyanthraquinone is also studied. Effect of different alcohols (hydrogen-bonding agents) and organic acids (protonating agents) on the CVs and SWVs of 1,2-dihydroxyanthraquinone is also investigated. It is found that addition of alcohols shifts the peak potential of the dianion towards less negative potential whereas addition of organic acids) inhabits the formation of dianion. Furthermore, it is also observed that methanol has strong hydrogen-bonding interaction with 1,2-dihydroxyanthraquinone as compared to ethanol and propanol. The hydrogen bonding equilibrium constant and hydrogen-bonding rate constants are evaluated from the shift in CV curves using Gupta and Linchtiz equation. It is inferred that the anion radical has a very weak hydrogen bonding interaction with alcohols as compared to dianion.

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“…We surmise that the shoulder peak is not from a structurally new product, as our NMR studies pointed towards the absence of the formation of any new species that are structurally very distinct from DHAQ. The presence of this charge transfer complex 31,32 is evident from the GCD (Fig. S4†) and CV (Fig.…”