Microhydration of substituted diamondoid radical cations of biological relevance: infrared spectra of amantadine+-(H2O)n = 1–3 clusters
| Autor: | Friedrich Buttenberg, Martin Andreas Robert George, Otto Dopfer, Marko Förstel |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
education.field_of_study
010405 organic chemistry Ligand Hydrogen bond Dimer Population Photodissociation General Physics and Astronomy Infrared spectroscopy 010402 general chemistry 01 natural sciences 0104 chemical sciences chemistry.chemical_compound Crystallography chemistry Radical ion Reactivity (chemistry) Physical and Theoretical Chemistry education |
| Zdroj: | Physical Chemistry Chemical Physics. 22:28123-28139 |
| ISSN: | 1463-9084 1463-9076 |
| DOI: | 10.1039/d0cp05299j |
| Popis: | Hydration of biomolecules and pharmaceutical compounds has a strong impact on their structure, reactivity, and function. Herein, we explore the microhydration structure around the radical cation of the widespread pharmaceutical drug amantadine (C16H15NH2, Ama) by infrared photodissociation (IRPD) spectroscopy of mass-selected Ama+Wn = 1–3 clusters (W = H2O) recorded in the NH, CH, and OH stretch range of the cation ground electronic state. Analysis of the size-dependent frequency shifts by dispersion-corrected density functional theory calculations (B3LYP-D3/cc-pVTZ) provides detailed information about the acidity of the protons of the NH2 group of Ama+ and the structure and strength of the NH⋯O and OH⋯O hydrogen bonds (H-bonds) of the hydration network. The preferred sequential cluster growth begins with hydration of the two acidic NH protons of the NH2 group (n = 1–2) and continues with an extension of the H-bonded hydration network by forming an OH⋯O H-bond of the third W to one ligand in the first hydration subshell (n = 3), like in the W2 dimer. For n = 2, a minor population corresponds to Ama+W2 structures with a W2 unit attached to Ama+via a NH⋯W2 H-bond. Although the N–H proton donor bonds are progressively destabilized by gradual microhydration, no proton transfer to the Wn solvent cluster is observed in the investigated size range (n ≤ 3). Besides the microhydration structure, we also obtain a first impression of the structure and IR spectrum of bare Ama+, as well as the effects of both ionization and hydration on the structure of the adamantyl cage. Comparison of Ama+ with aliphatic and aromatic primary amine radical cations reveals differences in the acidity of the NH2 group and the resulting interaction with W caused by substitution of the cycloalkyl cage. |
| Databáze: | OpenAIRE |
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