On the applicability of density functional theory to manganese‐based complexes with catalytic activity toward water oxidation

Abstract

The present contribution assesses the performance of several popular and accurate density functionals, namely B3LYP, BP86, M06, MN12L, mPWPW91, PBE0, and TPSSh toward manganese-based coordination complexes. These compounds show promising properties toward application to catalytic water oxidation. Although manganese with N- and O-biding ligands tends to give rise to high spin complexes, the results show that BP86, mPWPW91, and specially MN12L, tend to yield low-spin complexes. The usage of these functionals for such compounds is, thus, discouraged. All the functionals considered deliver accurate geometries. The present results show, however, that B3LYP delivers geometries deviating from experimental values when compared to the other functionals of the set. M06, PBE0, and TPSSh deliver geometries of similar accuracy, PBE0 outstanding slightly with respect to the other two. © 2017 Wiley Periodicals, Inc.

Hydricity of 3d Transition Metal Complexes from Density Functional Theory: A Benchmarking Study

“…Based purely upon the MAEs obtained here, revPBE0 would be the functional of choice; however, we recommend to use PBE0 (based upon an improved performance over revPBE0 on geometries produced with the smaller def2-SVP basis, MAEs of 1.4 and 1.8 kcal/mol, see ESI Figure S7 and Section 3.3.2 ), which has been shown to perform well in many previous studies of TM systems [ 17 , 85 ] and in the differentiation of spin state energetics [ 17 ].…”

“…While low on the Jacob’s ladder of functionals, the pure GGA, BP86, has been shown to produce accurate energetics for the hydricity of 3d TM hydrides. The hybrid functional, PBE0 has also been shown to perform well and is recommended for energy calculations over BP86 due to the improved ability to more reliably differentiate between spin states of 3d TM complexes [ 17 ]. The lowest mean absolute errors were found with the inclusion of both dispersion corrections and implicit solvation.…”

“…M06 was selected for their work as the computed barrier heights were found to be closest to the average value across the functionals tested. A benchmarking study was performed by Gamez et al [ 17 ] on a number of high-spin Mn-based complexes using a range of different functionals. It was found that pure functionals (i.e., non-hybrid) favoured low-spin forms of these Mn complexes, with weak-field nitrogen and oxygen based ligands, experimentally known to be high-spin complexes.…”

Importance of Dispersion in the Molecular Geometries of Mn(III) Spin Crossover Complexes

“…Leitner and co-workers tried to address this issue by optimizing a series of manganese complexes with different coordination numbers and oxidation states. 22 They showed that, in some cases, metal complexes with weak ligand fields had serious errors in the geometries despite including the dispersion correction. They proposed that this could be due to the limitation of the density functionals to model dispersion beyond certain extent.…”

“…In some cases, the geometries are not significantly improved by including empirical dispersion corrections. 22 The challenge for transition metal complexes is that it is not obvious a priori which of these factors is impacting the quality of the DFT geometry. Said another way, it is not clear to what extent multiconfigurational character plays a role in a complex until one performs a calculation and analyzes it.…”