In search of the best DFT functional for dealing with organic anionic species

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

PHYSICAL CHEMISTRY CHEMICAL PHYSICS

ROYAL SOC CHEMISTRY

Año: 2017 vol. 19 p. 9189 - 9198

1463-9076

Quantum chemical computational methods arethought to have problems in dealing with unstable organic anions. This workassesses the ability of different Density Functional Theory (DFT) functionalsto reproduce electron affinity and reduction potential of organic compounds.The performance of 23 DFT functionals was evaluated computing negative electronaffinities (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 inthe prediction of electron affinities, being BPW91, B3PW91 and M06 the bests oneach class of functionals (pure, hybrid and meta-GGA functionals,respectively). On the other hand, the abinitio post Hartree-Fock methods, MP2 and coupled-cluster (CCSD(T)), aswell as the double hybrid functionals, B2PLYP, mPW2PLYP, usually fail. Forcompounds with EAs lower than -1.75eV, a method for stabilizing the anion, based on solvation with the IEFPCMmodel was employed. In this case, BPW91, PBE0 and M06-HF could be therecommended option for a pure, a hybrid and a meta-GGA functional,respectively. The situation improves for the evaluation and prediction of redoxpotentials. In this case the performance of the DFT functionals is better, inpart because the solvent assists 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 acancellation of errors. In this case, the hybrid and meta-GGA functionalsB3PW91, PBE0, TPSSh and M06 are also among the best for computing redoxpotentials with a mean absolute deviation (MAD) lower than 0.13 V.