A method to calculate the one-electron reduction potentials for nitroaromatic compounds based on gas-phase quantum mechanics.

Nitroaromatic compounds (NACs) are widespread environmental contaminants, and the one-electron reduction potential (E oH) is an important parameter used in modeling their environmental fate. We have identified a method that is both accurate and efficient to predict E oH values for NACs, using gas-phase quantum mechanics (QM) calculations combined with empirical correlations. First, the adiabatic electron affinity (EA) at 0 K is calculated using the B98/MG3S method, and the predictions are scaled by a factor of 0.802 to account for systematic errors in the density functional calculations. Second, the E oH values are predicted from a linear correlation between E oH and EA. Using this method, E oH values were predicted with a mean absolute deviation from measured values of 0.021 V for the 14 NACs used to obtain the correlation and 0.029 V for six additional NACs. This represents a substantial improvement in accuracy over predictions by other QM methods, which are affected by large errors in solvation or aqueous-phase calculations for some compounds.