Cooperativity of intermolecular hydrogen bonds in microsolvated DMSO and DMF clusters: a DFT, AIM, and NCI analysis

Density functional theory (DFT) calculations are performed to study the hydrogen-bonding in the DMSO-water and DMF-water complexes. Quantitative molecular electrostatic potential (MESP) and atoms-in-molecules (AIM) analysis are applied to quantify the relative complexation of DMSO and DMF with water molecules. The interaction energy of DMSO with water molecules was higher than in DMF-water complexes. The existence of cooperativity effect helps in the strong complex formation. A linear dependence was observed between the hydrogen bond energies EHB, and the total electron densities in the BCP's of microsolvated complexes which supports the existence of cooperativity effect for the complexation process. Due to the stronger DMSO/DMF and water interaction, the water molecules in the formed complexes have a different structure than the isolated water clusters. NCI analysis shows that the steric area is more pronounced in DMF-water complex than the DMSO-water complex which accounts for the low stability of DMF-water complexes compared to the DMSO-water complex.