Method for the accurate prediction of electron transfer potentials using an effective absolute potential

Area of Science:

• Computational chemistry
• Physical chemistry
• Quantum chemistry

Background:

• Electron transfer (ET) potentials are crucial for understanding redox reactions.
• Accurate computation of ET potentials is challenging due to reliance on absolute potential values.
• Existing methods often use a fixed absolute potential, leading to inaccuracies.

Purpose of the Study:

• To develop a protocol for accurate computation of electron transfer potentials.
• To establish a method for calculating computational setup-dependent effective absolute potentials.
• To improve the prediction accuracy of ET potentials for organic molecules.

Main Methods:

• Utilizing experimental pKa values to compute effective absolute potentials.
• Employing ab initio and density functional theory (DFT) calculations.
• Comparing results from various computational setups, including CCSD(T) and DFT functionals like M06-2X.

Main Results:

• The protocol yields effective absolute potentials that vary significantly between computational setups.
• The most accurate estimate for the normal hydrogen electrode (nhe) in water is 4.14 V (using CCSD(T)/aug-ccpvqz).
• Accurate ET potential predictions were achieved for organic molecules with a standard deviation of 0.13 V using CCSD(T).
• The effective absolute potential method performed comparably or better than literature values for DFT functionals, with M06-2X achieving a standard deviation of 0.18 V.

Conclusions:

• The developed protocol provides a more accurate approach to calculating electron transfer potentials.
• Using method-specific effective absolute potentials enhances prediction accuracy.
• This method offers a significant improvement for computational studies of redox processes.