?The Palme d?Or goes to ??. A search for the best functional for dealing with anionic organic species?

MARCELO PUIATTI

Lyon

Conferencia; Workshop Electron Transfer, Radical Ions and Radical Chemistry ETRADCHEM; 2017

During the last few decades, density functional theory (DFT) has become the method of choicein quantum chemical studies. Indeed, many experimental investigations routinely include suchcalculations, using a popular code, a standard basis, and a standard functional approximation. 1 It iswell known that DFT has provided approximations that work quite well for some problems and failfor others. 2 Hence, a proper recommendation should be to search for the DFT functional that worksbetter within the problem to be studied. In the present study we addressed the overall performanceof 23 different DFT functionals and ab initio methods for studying anionic organic species.In order to evaluate its scope and limitations, electron affinities (EA) and reduction potentials (were computed. A set of 60 molecules was employed for the calculation of EAs, in the range of 0 to-3.4 eV. Besides, 62 compounds were selected for the computation of the , with potentials,measured in acetonitrile, from -2.71 V to 0.06 V (vs. standard hydrogen electrode, SHE).For compounds with negative EAs, hybrid GGA gave better results than pure and meta GGA.Double hybrid functionals and ab initio methods yield poorly with MADs higher than 0.5 eV.The calculations of are strongly dependent on the quality of the solvation energies of thecharged species. This was evidenced in the correlation of calculated absolute vs. experimental .However, there is a significant improvement after the use of a proper redox partner. The best resultswere obtained with hybrid GGA functionals, B3PW91 and PBE0. TPSSh and M06 were the bettermeta GGA. Pure GGA functionals gave good results, with low dispersion, but high MADs, thatcould improve by choosing a proper reference.The ideal scenario should give a podium with some functionals that outperform the others.However, there is a suitable DFT functional for each problem instead of a universal one that couldsolve almost all the situations within different conditions.References:1- Burke, K., J Chem Phys, 2012, 136, 150901.2- Medvedev, M. G.; Bushmarinov, I. S.; Sun, J.; Perdew, J. P.; Lyssenko, K. A. Science, 2017, 355, 49-52.