Structural characterization in solution of multifunctional nucleotide coordination systems

The interaction in aqueous solution of the cyclophane receptors 2,6,10,13,17,21-hexaaza[22]orthocyclophane (L-1) and 2,6,10,13,17,21-hexaaza[22]paracyclophane (L-2) with the nucleotides ATP, ADP and AMP has been studied by pH titration and NMR. The obtained results are compared with those previously reported for the analogous meta-substituted receptor 2,6,10,13,17,21-hexaaza[22]metacyclophane (L). All the experimental data support the actuation of these cyclophane molecules as multi-point binders of nucleotides through electrostatic, hydrogen bonding and pi-stacking interactions. The combined use of NMR and molecular dynamics permits us to get a rather reliable picture of the way in which the molecules organise in solution and how the intermolecular interactions (electrostatics, hydrogen bonding, pi-stacking) are established.