Ab initio molecular dynamics investigation of proton delocalization in crown ether complexes with H3O+ and NH4 (+)

作者：Bendiab W Taleb; Reguig F Hamza; Hamad S; Martinez Haya B; Krallafa A M^*

来源：Journal of Inclusion Phenomena and Macrocyclic Chemistry, 2016, 85(1-2): 83-92.

DOI：10.1007/s10847-016-0607-2

• Ab initio molecular dynamics
• IRMPD spectra
• Vibrational spectroscopy
• Crown ether
• Host-guest interactions
• Proton delocalization

The simple structure of crown ethers has found a wide range of applications in macrocyclic chemistry, largely due to its ability to capture positively charged ions either in atomic or molecular state. In the present work, ab initio molecular dynamics calculations are performed to characterize the host-guest interactions and conformational dynamics of the complexes formed by the H3O+ and NH4 (+) cations with the native crown ethers 15-crown-5 and 18-crown-6. A particular focus is set on the proton delocalization effects unveiled in recent spectroscopy experiments for some of these complexes under well-defined isolated (solvent-less) conditions. The calculations confirm that the infrared signature of these benchmark crown ether complexes provides a sensitive probe for proton delocalization. The ab initio study also shows that proton delocalization occurs for the H3O+ host (and not for NH4 (+)), provided that the size of the crown ring allows for tight H-bonding interactions between the cationic guest and the crown ether, leading short H2O center dot center dot center dot H+center dot center dot center dot O (crown) bonds.

• 出版日期2016-6