Electrostatic insights into the molecular hydration process: a case study of crown ethers

Abstract

Ab initio quantum chemical methods as well as simulation/dynamics programs have been conventionally used for probing the hydration of molecules, an important problem in chemistry and biology. However, very few attempts have as yet been reported for understanding the stepwise patterns in hydration processes at the molecular level. The present work investigates the problem of hydration of the 18-crown-6 (18C6) molecule based on rigorous topography mapping of molecular electrostatic potential (MESP) followed by an application of a simple electrostatic model (electrostatic potential for intermolecular complexation) for obtaining trends in energetics. Structures and energies of the hydrated species, 18C6.nH₂O (n = 1, 2, 3, 4, 6) have been studied by the EPIC model followed by ab initio HF/6-31G^∗∗ investigations. The remarkable agreement between the model and ab initio results highlights the utility of MESP topography for exploring the lock-and-key features in a hydration process via cooperative electrostatic effects.