Assessing the Quality of QM/MM Approaches to Describe Vacuo-to-water Solvatochromic Shifts

TL;DR

This paper evaluates various QM/MM embedding models for predicting solvatochromic shifts from vacuum to water, highlighting that no single approach is universally best and errors depend on molecular specifics.

Contribution

It systematically compares polarizable and non-polarizable QM/MM models against experimental data, revealing the importance of system-specific model selection.

Findings

No approach consistently outperforms others.

Errors vary significantly with molecular transition type.

Black-box application of a single model can lead to inaccuracies.

Abstract

The performance of different Quantum Mechanics/Molecular Mechanics embedding models to compute vacuo-to-water solvatochromic shifts are investigated. In particular, both non-polarizable and polarizable approaches are analyzed and computed results as compared to reference experimental data. We show that none of the approaches outperforms the others and that errors strongly depend on the nature of the molecular transition. Thus, we prove that the best choice of embedding model highly depends on the molecular system, and that the use a specific approach as a black-box can lead to significant errors and sometimes totally wrong predictions.