Dispersion-Corrected DFT Study of Uracil-5Water (U5W) Complexes: Energetic, Structures, Vibrational Properties, and Solvatochromic Shifts

Understanding uracil solvation is crucial for refining hydrogen bonding (H-bonding) models in aqueous systems, with implications for enzyme activity and drug design. In this study, we investigate novel uracil-5water (U5W) complexes, revealing an unusual H-bond arrangement that significantly influences vibrational properties. Density functional theory (DFT) calculations using ωB97XD and CAM-B3LYP-D3 functionals with various basis sets identified the most stable isomers (U11333, U11133, U12223), characterized by clustered water molecules and optimal H-bond lengths. New isomers (U11134, U11144, U11124) exhibited enhanced stability compared to previously reported configurations. Vibrational mode analysis confirmed hydration effects, notably influencing ν(N-H) and ν(C2=O) shifts. The U12223 complex displayed a distinct N3H···Ow bond, altering vibrational behavior. These findings provide insights into H-bonding interactions and molecular stability, paving the way for future theoretical and experimental studies.