Water: new aspect of hydrogen bonding in the solid state

Area of Science:

• Crystallography
• Computational Chemistry
• Physical Chemistry

Background:

• Water-water interactions are fundamental to molecular structure and chemistry.
• Classical hydrogen bonding criteria may not encompass all attractive water interactions.

Purpose of the Study:

• To identify and analyze all water-water contacts in crystal structures.
• To investigate attractive interactions beyond classical hydrogen bonds.
• To propose broader geometric criteria for defining water-water interactions.

Main Methods:

• Analysis of water-water contacts (d_OO ≤ 4.0 Å) from the Cambridge Structural Database.
• Geometric analysis and interaction energy calculations using CCSD(T)/CBS.
• Development of geometric criteria for antiparallel dipolar interactions.

Main Results:

• Identified 6729 attractive water-water contacts, with 4717 classical hydrogen bonds.
• Discovered 2062 additional attractive interactions, predominantly antiparallel dipolar.
• Characterized 1282 antiparallel dipolar contacts with interaction energies up to -4.7 kcal/mol.

Conclusions:

• Attractive water-water interactions extend beyond classical hydrogen bonds.
• Antiparallel dipolar interactions represent a significant class of attractive forces.
• Broader geometric criteria are needed to fully appreciate water-water interactions in molecular systems.