We report the redox potentials of a set of organic aryl molecules, including quinones, juglone, tyrosine and tryptophan, calculated using a first principles molecular dynamics (FPMD) based method. The hybrid functional HSE06 reproduces the redox potentials spanning from -0.25 V to 1.15 V within an error of 0.2 V, whereas the errors with the BLYP functional are much larger (up to 0.7 V). It is found that the BLYP functional predicts consistently lower electron affinities/ionization potentials than HSE06 both in gas phase and in an aqueous solution. In water, the ionization potentials are significantly underestimated by BLYP due to the exaggeration of the mixing between the solute states and the valence band states of liquid water. Hybrid HSE06 markedly improves both the solute levels and water band positions, leading to accurate redox potentials. This study suggests that the current FPMD based method at the level of hybrid functionals is able to accurately compute the redox potentials of a wide spectrum of organic molecules.
We acknowledge the National Science Foundation of China (No.
41222015, 41273074, 41572027 and 21373166), Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund (the second phase), the Foundation for the Author of National Excellent Doctoral Dissertation of P. R. China (No. 201228), Newton International Fellowship Program and the financial support from the State Key Laboratory at Nanjing University. We are grateful to the High Performance Computing Center of Nanjing University for allowing us to use the IBM Blade cluster system.
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