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

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.