Structure of Amido Pyridinium Betaines: Persistent Intermolecular C−H⋅⋅⋅N Hydrogen Bonding in Solution |
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| Authors: | Dr Robert J Thatcher Dr David G Johnson Dr John M Slattery Dr Richard E Douthwaite |
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| Affiliation: | Department of Chemistry, University of York, Helsington, York, UK |
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| Abstract: | A hydrogen bond of the type C?H???X (X=O or N) is known to influence the structure and function of chemical and biological systems in solution. C?H???O hydrogen bonding in solution has been extensively studied, both experimentally and computationally, whereas the equivalent thermodynamic parameters have not been enumerated experimentally for C?H???N hydrogen bonds. This is, in part, due to the lack of systems that exhibit persistent C?H???N hydrogen bonds in solution. Herein, a class of molecule based on a biologically active norharman motif that exhibits unsupported intermolecular C?H???N hydrogen bonds in solution has been described. A pairwise interaction leads to dimerisation to give bond strengths of about 7 kJ mol?1 per hydrogen bond, which is similar to chemically and biologically relevant C?H???O hydrogen bonding. The experimental data is supported by computational work, which provides additional insight into the hydrogen bonding by consideration of electrostatic and orbital interactions and allowed a comparison between calculated and extrapolated NMR chemical shifts. |
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| Keywords: | aggregation betaines bond energy hydrogen bonds nitrogen heterocycles |
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