Experimental and Theoretical Reduction Potentials of Some Biologically Active ortho-Carbonyl para-Quinones.

Maximiliano Martínez-Cifuentes,Oney Ramírez-Rodríguez,Boris Weiss-López,Ricardo Salazar,Ramiro Araya-Maturana

doi:10.3390/molecules22040577

Abstract

The rational design of quinones with specific redox properties is an issue of great interest because of their applications in pharmaceutical and material sciences. In this work, the electrochemical behavior of a series of four p-quinones was studied experimentally and theoretically. The first and second one-electron reduction potentials of the quinones were determined using cyclic voltammetry and correlated with those calculated by density functional theory (DFT) using three different functionals, BHandHLYP, M06-2x and PBE0. The differences among the experimental reduction potentials were explained in terms of structural effects on the stabilities of the formed species. DFT calculations accurately reproduced the first one-electron experimental reduction potentials with R2 higher than 0.94. The BHandHLYP functional presented the best fit to the experimental values (R2 = 0.957), followed by M06-2x (R2 = 0.947) and PBE0 (R2 = 0.942).

Highlights

The quinone/semiquinone/hydroquinone (Q/SQ− /HQ) triad, ubiquitous in nature, is an important part of many redox systems in biology, acting as a vital link in electron transfer processes through both mitochondria and chloroplasts [1]
We studied the electrochemical reduction of two benzoquinones bearing vicinal carbonyl and alkyl groups linked by a double bond (Figure 1)
The first process can be associated with the addition of one electron to the quinone species to form the semiquinone anion radical (SQ− ), and the second wave could be associated with the addition of another electron to form the hydroquinone di-anion (HQ−2 )

Summary

Introduction

The quinone/semiquinone/hydroquinone (Q/SQ− /HQ) triad, ubiquitous in nature, is an important part of many redox systems in biology, acting as a vital link in electron transfer processes through both mitochondria and chloroplasts [1]. The redox couple Q/HQ can directly interconvert through other enzymatic systems via a two-electron process [2]. An important characteristic of quinones is their capability to undergo reversible oxidation-reduction reactions [3]. Besides the importance of the Q/HQ couple as anticancer agents [7,8,9,10] antifungal [11,12], and antiparasitic drugs [13], the quinone motif is found in many dangerous xenobiotics, such as carcinogenic polyaromatic quinones generated in air-suspended particulate by oxidation of polycyclic aromatic hydrocarbons [14]. Q/HQ derivatives have gained growing interest in the development of new organic materials, in areas such as solar energy conversion, [15]

Methods

Results

Conclusion