Specific hydration effects on oxo-thio triazepine derivatives

Area of Science:

• Computational Chemistry
• Molecular Modeling
• Quantum Chemistry

Background:

• 2,7-dimethyl-1,2,4-triazepine oxo-thio derivatives possess multiple hydrogen bond (HB) donor and acceptor sites.
• Understanding hydration is crucial for predicting molecular behavior and interactions.

Purpose of the Study:

• To investigate the specific hydration of 2,7-dimethyl-1,2,4-triazepine oxo-thio derivatives by a single water molecule.
• To identify the most stable hydration complexes and analyze the nature of hydrogen bonds formed.

Main Methods:

• Density Functional Theory (DFT) calculations using the B3LYP functional with the 6-311++G(3df,2p)//B3LYP/6-311+G(d,p) basis set.
• Analysis of hydrogen bond types (CH-O, OH-S, NH-O, OH-N, OH-O) and complex stability.
• Application of Atoms in Molecules (AIM) theory and Electron Localization Function (ELF) analysis to determine basicity sites.

Main Results:

• The most stable complexes involve heteroatoms at positions 3 and 5 acting as HB acceptors and the nitrogen at position 4 as the HB donor.
• Thiocarbonyl groups form stronger HBs than carbonyl groups, with sulfur being a better HB acceptor than oxygen.
• Basicity analysis revealed that heteroatom at position 3 is the most basic site in 3O5O, 3S5O, and 3S5S, while sulfur is the most basic in 3O5S.

Conclusions:

• The study elucidates the preferred hydration sites and hydrogen bonding patterns in these triazepine derivatives.
• Computational methods provide valuable insights into the intermolecular interactions governing the stability of hydrated molecular systems.
• The findings highlight the significant role of sulfur in enhancing hydrogen bonding interactions compared to oxygen in these systems.