title: Structure of Amido Pyridinium Betaines: Persistent Intermolecular C-H⋅⋅⋅N Hydrogen Bonding in Solution.
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-1per 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.
authors.affiliation: Department of Chemistry, University of York, Helsington, York, YO10 5DD, UK.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Thatcher
authors.affiliation: Department of Chemistry, University of York, Helsington, York, YO10 5DD, UK.
authors.forename: David G
authors.initials: DG
authors.lastname: Johnson
authors.affiliation: Department of Chemistry, University of York, Helsington, York, YO10 5DD, UK. richard.douthwaite@york.ac.uk.
authors.forename: John M
authors.initials: JM
authors.lastname: Slattery
authors.affiliation: Department of Chemistry, University of York, Helsington, York, YO10 5DD, UK. john.slattery@york.ac.uk.
authors.forename: Richard E
authors.identifier: http://orcid.org/0000-0002-8423-7528
authors.initials: RE
authors.lastname: Douthwaite
keywords: aggregation; betaines; bond energy; hydrogen bonds; nitrogen heterocycles