Dynamic solvation fields: a paradigm shift in solvent effects on chemical reactivity

Traditional solvent descriptors-such as dielectric constant, donor number, or polarity scales-reduce complex, fluctuating environments to static averages. While valuable for capturing bulk trends, these parameters fail to account for the localized, time-resolved interactions that govern many chemical transformations. This perspective argues for a conceptual shift: treating solvents as dynamic solvation fields, characterized by fluctuating local structure, evolving electric fields, and time-dependent response functions. Drawing on a synthesis of experimental, computational, and theoretical work from 2015-2025, we show how solvent dynamics modulate transition state stabilization, steer nonequilibrium reactivity, and reshape interfacial chemical processes. We critically examine the limitations of continuum and linear-response models and highlight emerging tools-from ultrafast spectroscopy to machine-learned potentials-that expose the active role of the solvent in chemistry. Finally, we propose a conceptual framework for a general theory of dynamic solvation fields, with implications for catalysis, nucleation, and thin-film formation. This approach offers a more faithful and predictive understanding of solvent effects in modern physical chemistry.