Application of Density Functional Theory for evaluation of standard two-electron reduction potentials in some quinone derivatives

In this research, two-electron reduction potentials are calculated for a set of eight quinones using Density Functional Theory (DFT) at B1B95/6-31G∗∗ and B1B95/6-311++G∗∗ levels in aqueous solution. Two different mechanisms, direct and indirect, which have been presented before, are employed for these calculations. DPCM and CPCM models of solvation are carried out to include solution phase contribution. The results show that CPCM is properly matched with DFT method at the B1B95 level in both direct and indirect mechanisms. It is found that direct mechanism gives more accurate two-electron reduction potentials in comparison to indirect mechanism. Mean Absolute Deviation (MAD) obtained through indirect mechanism and CPCM model of solvation are about 0.041 and 0.022 V for 6-31G∗∗ and 6-311++G∗∗, respectively. The MAD values of direct mechanism are about 0.024 and 0.018 V for 6-31G∗∗ and 6-311++G∗∗ basis sets, respectively. The calculated MAD for both direct and indirect mechanisms is comparable with MAD previously reported at MP3 level for this set of molecules.