Tautomeric self-dimerization and molecular recognition properties of 2-aminopyrimidinone derivatives as triple hydrogen-bonding modules in molecular assemblies

A triple hydrogen-bonding module based on 6-alkynyl-2-amino-3H-pyrimidin-4- one was developed such as for self-dimerization and for nucleobase recognition processes. The strength of the module for the self-dimerization was determined by NMR and fluorimetric analyses in chloroform (ΔG₂₉₈ = -22 to -23 kJ/mol). DFT calculations and X-ray structure analysis showed that the self-dimerization consists of the three-point hydrogen-bonding including two kinds of tautomers of the module in an ADD·DAA mode. Selective recognition of the module for a cytidine derivative was also observed, and the free energy change for the complexation (ΔG₂₉₈ = -31 kJ/mol) is one of the highest values among triple hydrogen-bonded complexes so far reported.