Stochasticity of Solvent Dynamics: Why Dipoles Emerge Where No Dipoles Are Expected?

Abstract

Electric dipoles are ubiquitous, and they are unequivocally important for vital processes in nature and in manmade devices. A recent examination of the dipole dynamics of molecular electrets (i.e., macromolecules with ordered electric dipoles) reveals enormous picosecond fluctuations ranging from 50% to 200% of the average magnitudes. Herein, we demonstrate their universality by exploring the dipole dynamics of aromatic molecules by using polarizable molecular dynamics and quantum mechanical calculations. Explicit solvent implementation leads to not only large fluctuations of the dipoles of polar species, such as coumarin 102, but also the emergence of fluctuating dipoles of nonpolar polycyclic aromatic hydrocarbons (PAHs), such as pyrene and pentacene. For the nonpolar PAHs in polar solvents, the magnitude of the dipole transients reaches up to 5 D. These results demonstrate key paradigms of fluctuating localized electric fields emerging from solvation dynamics with major implications for charge transfer, catalysis, energy conversion, and enzymatic transformations, among other phenomena.