Direct Detection of Hydrogen Bonds in Supramolecular Systems Using 1H-15N HMQC

Hydrogen-bonded supramolecular systems are usually characterized in solution through analysis of NMR data such as complexation induced shifts and nuclear Overhauser effects (nOe). Routine direct detection of hydrogen-bonding particularly in multicomponent mixtures, even with the aid of 2D NMR experiments for full assignment, is more challenging. We describe an elementary rapid 1H-15N HMQC NMR experiment which addresses these challenges without the need for complex pulse sequences. Under readily accessible conditions, (243/263 K, 50 mmol solutions) and natural 15N abundance, un-ambiguous assignment of 15N resonances facilitates direct detection of intra- and intermolecular hydro-gen-bonds in mechanically interlocked structures and quadruply hydrogen-bonded dimers – of dialkylureidopyrimidinones (AUPy), Ureidopyrimidinones (UPy), and diamidonaphthyridines (DAN) – in single or multicomponent mixtures to establish tautomeric configuration, conformation, and, to resolve self-sorted speciation.