Exploring Solvation Effects in Ligand-Exchange Reactions via Static and Dynamic Methods

Abstract

We investigate ligand-exchange reactions of a biomimetic Co(II)-based heterocubane complex in aqueous solution by means of various approaches for consideration of solvent effects. Static calculations based on geometry optimizations carried out in vacuum, with solvent continuum models, or with several explicit solvent molecules have been carried out as well as density functional theory (DFT)-based molecular dynamics simulations. In addition, reaction pathways and barriers have been elucidated via nudged elastic band calculations and metadynamics. The results show that static approaches with approximate consideration of the solvent environment lead to reaction energies, which may change drastically depending on the method employed. A more sophisticated approach is DFT-molecular dynamics at ambient conditions with full solvation, i.e. enough solvent molecules to retain bulk water properties far from the solute, which, however, comes with a much higher computational cost. The investigated example of the exchange of an acetate ligand by a hydroxide demonstrates that entropic contributions can be vital and consideration of electronic energies alone may be a rather rough approximation.

Discovery of Open Cubane Core Structures for Biomimetic LnCo3(OR)4 Water Oxidation Catalysts

“…In the following section, we will address the effects of the solvation model on the different structures . An inherent problem of many implicit solvent models (such as COSMO) is their inability to accurately describe directed bonds such as hydrogen bonds between solute and solvent.…”

“…Going beyond solvent continuum models in analogy to previous work, the structures were also modeled with an explicit first solvation shell derived from a DFT‐based MD run (see section Methods for details). A detailed description of the structures can be found in the Supporting Information (section on Structural Analysis of Explicit Solvation).…”

“…The existence of many shallow local minima on the potential energy surface makes the comparison of energies a tedious task as one has to be sure to compare the same local minima with respect to the solvation shell. To get a more accurate description of explicit solvation approaches, sampling methods such as DFT‐based MD might be used as described elsewhere . Nevertheless, such methods are significantly more expensive in terms of computational cost and beyond the scope of this work.…”

Metadynamics for automatic sampling of quantum property manifolds: exploration of molecular biradicality landscapes

“…for investigation of folding mechanisms in proteins, 21 while studies based on quantum chemical metadynamics simulations are still relatively rare. 22,23 To the best of our knowledge, we have recently published a first multistate formulation of the quantum chemical metadynamics, capable of the automatic localization of conical intersections in molecular systems. The algorithm is available through the metaFALCON program package.…”

Advancing Computational Approaches for Study and Design in Catalysis

“…[7] With increasing numbers of solvent molecules, this approach reaches its limitation. [5,[7][8][9] AIMD allows sampling over different configurations and a sophisticated description of condensed phase systems (such as liquids), usually by means of periodic boundary conditions (see Fig. 2).…”