In search of the best DFT functional for dealing wi th organic anionic species .

BORIONI, JOSÉ L.; M. PUIATTI; D. M. A. VERA; ADRIANA B. PIERINI

PHYSICAL CHEMISTRY CHEMICAL PHYSICS

ROYAL SOC CHEMISTRY

Lugar: CAMBRIDGE; Año: 2017 vol. 19 p. 9189 - 9198

1463-9076

Quantum chemical computational methods are thought to have problems in dealing with unstable organicanions. This work assesses the ability of different Density Functional Theory (DFT) functionals to reproduce electronaffinity and reduction potential of organic compounds. The performance of 23 DFT functionals was evaluated computingnegative electron affinities (from 0 eV to -3.0 eV) and reduction potentials in acetonitrile (from 0 to -2.7 V). In general,most of the hybrid GGA functionals work fine in the prediction of electron affinities, being BPW91, B3PW91 and M06 thebests on each class of functionals (pure, hybrid and meta-GGA functionals, respectively). On the other hand, the ab initiopost Hartree-Fock methods, MP2 and coupled-cluster (CCSD(T)), as well as the double hybrid functionals, B2PLYP,mPW2PLYP, usually fail. For compounds with EAs lower than -1.75 eV, a method for stabilizing the anion, based onsolvation with the IEFPCM model was employed. In this case, BPW91, PBE0 and M06-HF could be the recommendedoption for a pure, a hybrid and a meta-GGA functional, respectively. The situation improves for the evaluation andprediction of redox potentials. In this case the performance of the DFT functionals is better, in part because the solventassists in the stabilization of the anions. Nevertheless, there is a systematic bias in the calculations of absolute redoxpotentials it could be corrected by using a redox partner that helps by a cancellation of errors. In this case, the hybrid andmeta-GGA functionals B3PW91, PBE0, TPSSh and M06 are also among the best for computing redox potentials with amean absolute deviation (MAD) lower than 0.13 V.