Hydration effect on proton transfer in melamine-cyanuric acid complex.

Area of Science:

• Computational Chemistry
• Materials Science
• Biochemistry

Background:

• Melamine-cyanuric acid (MC) self-assembly is linked to urinary tract calculi and renal failure.
• Understanding MC complex behavior is crucial for preventing kidney stone formation.

Purpose of the Study:

• To investigate the hydration effects on the molecular geometry, IR spectra, frontier molecular orbital, proton transfer (PT) energy barrier, and stability of melamine-cyanuric acid (MC) complexes.
• To elucidate the mechanisms of intramolecular and intermolecular proton transfer in MC complexes under varying hydration conditions.

Main Methods:

• Density Functional Theory (DFT) calculations were employed to explore hydration effects.
• Analysis included molecular geometry, IR spectra, frontier molecular orbitals, and energy barriers for proton transfer.
• Simulations considered anhydrous and trihydrated MC clusters.

Main Results:

• Proton transfer (PT) in MC complexes was analyzed, revealing distinct changes in conjugation and hydrogen bonding upon intramolecular and intermolecular PT.
• Hydration significantly alters local geometry and IR spectra of hydrogen bonds.
• Hydration dramatically lowers the intramolecular PT barrier (from ~45 to ~11.5 kcal mol(-1)) while having a slight effect on the intermolecular PT barrier.

Conclusions:

• Proton transfer in MC complexes is sensitive to hydration, with significant reduction in the intramolecular PT barrier.
• Hydration is expected to inhibit the formation of specific MC aggregate structures (rosette-like and tape conformers).
• The study provides a molecular-level understanding of hydration's role in MC complex stability and reactivity, relevant to kidney stone pathogenesis.