I am trying to investigate a hydride transfer reaction of a transition-metal complex like the following:

$$ \ce{[M]-H + Ph3C+ -> [M]+ + Ph3CH} $$

For this I want to investigate the influence of solvation on the qualitative free Gibbs energies of the reaction. However, I am unsure about the proper procedure. These options come to mind:

  • Single-Point calculation of the gas-phase structure with added solvation model + using the thermochemical corrections from the gas-phase
  • Re-optimizing the gas-phase structure with added solvation model + new frequency calculation to obtain the thermochemical corrections

A look through literature did not really reveal a best-practice way on how to handle this. Would there be anything wrong with either procedure?

  • 3
    $\begingroup$ I would go by the second route, because solvent phase geometries are often different than gas phase. Not sure if there is any benchmark in literature over this. $\endgroup$
    – S R Maiti
    Commented Dec 20, 2022 at 11:00
  • $\begingroup$ Yeah, that was my initial idea. Unfortunately, with SMD I do not get convergence for my transition-metal complexes. I've read multiple times that PCM might not be the best choice for charged species. $\endgroup$
    – O2_AC
    Commented Dec 20, 2022 at 12:13
  • $\begingroup$ Which software are you using? Try solvent-accessible surface with SMD, it makes the PES smoother, and sometimes helps in convergence. $\endgroup$
    – S R Maiti
    Commented Dec 21, 2022 at 7:13
  • $\begingroup$ I'm using Gaussian16, I'll look into your suggestion, thanks. $\endgroup$
    – O2_AC
    Commented Dec 21, 2022 at 11:04
  • $\begingroup$ @SRMaiti I checked the Gaussian documentation, however, it states that the Solvent Accessible Surface option should only be used for Single Point calculations. $\endgroup$
    – O2_AC
    Commented Dec 21, 2022 at 13:31


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