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Published on: March 24, 2018
Theoretical study of imidazole...NO complexes.
Rachel Crespo-Otero1, Kenny Bravo-Rodríguez, Reynier Suardíaz
1Laboratorio de Química Computacional y Teórica, Facultad de Química, Universidad de la Habana, 10400 Havana, Cuba.
Protonation of imidazole significantly stabilizes its weak complexes with nitric oxide, particularly in planar arrangements. These interactions are confirmed as hydrogen bonds, with charge transfer playing a key role in stabilization.
Area of Science:
- Computational Chemistry
- Molecular Interactions
- Biophysical Chemistry
Background:
- Imidazole is a crucial biological molecule, and its interactions with nitric oxide (NO) are relevant in biological systems.
- Protonation state of imidazole can significantly alter its chemical properties and interactions.
Purpose of the Study:
- To investigate the structural and energetic properties of weak complexes formed between imidazole (Imi) and nitric oxide (NO).
- To evaluate the effect of imidazole protonation on the stability and nature of these complexes.
Main Methods:
- Quantum chemical calculations using UMP2/6-31++G(d,p) and UMP2/6-311++G(2d,2p) levels of theory.
- Analysis of both planar and nonplanar complex geometries.
- Application of Koch and Popelier criteria based on Atoms in Molecules (AIM) theory to identify hydrogen bonds.
Main Results:
- Protonation of imidazole (ImiH(+)) enhances the stability of planar NO...ImiH(+) complexes compared to neutral Imi complexes.
- Nonplanar complexes showed less significant changes in stability upon protonation.
- Analysis confirmed the presence of hydrogen bonds (Z-H...XY type) and highlighted the importance of charge transfer in stabilizing these complexes.
Conclusions:
- Imidazole protonation plays a critical role in stabilizing weak interactions with nitric oxide, especially in planar configurations.
- The findings provide insights into the molecular mechanisms governing imidazole-nitric oxide interactions in biological contexts.
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