Theoretical Exploration of 2,2’-Bipyridines as Electro-Active Compounds in Flow Batteries

Molecular information in SMILES code was used as input in Open Babel 2.4.0 \cite{O'Boyle2011} to find the minimum energy conformer using the MMFF94 force field. The generated geometries provided the cartesian coordinates that were used to generate a Gaussian input file. In some cases, it was necessary to apply a preliminary minimization using pseudopotentials (PM7) before performing the actual DFT calculation. Molecular energies of the 156 2,2'-bipirydines were obtained using the Gaussian 16 suite at DFT, with B3LYP hybrid functional and 6-31G(d) basis. Analysis of vibrational frequencies was performed to verify the existence of an energy minimum. All geometries were optimized using both the polarizable continuum model (PCM) \cite{Miertus1981,Scalmani2010} and the solvation model based on density (SMD) \cite{Marenich2009} with water as solvent; the results presented below correspond to SMD as it is better correlated with experimental values