Cyclen-based bismacrocycles for biological anion recognition. A potentiometric and NMR study of AMP, ADP and ATP nucleotide complexation.

The behaviour of two cyclen-based bismacrocycles linked by aromatic spacers as receptors of adenosine monophosphate (AMP), adenosine diphosphate (ADP) and adenosine triphosphate (ATP) anions is explored. The two bismacrocycles differ from one another by the nature of their spacers, which are respectively 1,3-dimethylbenzene (BMC), or 2,6-dimethylpyridine (BPyC). Potentiometric investigations supported by (1)H and (31)P NMR measurements were performed over a wide pH range to characterize and understand the driving forces implicated in the supramolecular assemblies. A comparison is also carried out with the results presented in this work and those obtained previously with these two ligands and inorganic phosphates. The comparison exhibits the importance of pi-stacking capability of the organic anions in the binding and hydrogen-bonding network. For BPyC, NMR studies highlight two coordination schemes depending on the protonation of the nitrogen atom of the pyridinyl spacer, which acts in acidic media as a supplementary anchoring point.