1,10-Dimethyl-1,4,7,10,13,16-hexaazacyclooctadecane (L) and 1,4,7-Trimethyl-1,4,7,10,13,16-hexaazacyclohenicosane (L1): two new macrocyclic receptors for ATP binding. Synthesis, and solution equilibria and the crystal structure of (H4L)(ClO4)4

The synthesis of two new methylated ligands 1,10-dimethyl-1,4,7,10,13,16-hexaazacyclooctadecane L and 1,4,7-trimethyl-1,4,7,10,13,16,19-heptaazacyclohenicosane L1 is described. Basicity constants and protonation enthalpies of both ligands have been determined by potentiometric and microcalorimetric measurements in 0.15 mol dm(-3) NaClO4 at 298.1 K. The protonated forms of these cyclic polyamines bind ATP in solution. The equilibrium constants of the species formed have been determined (0.15 mol dm(-3) NaClO4, 298.1 K). The results presented for L and L1 are compared with those previously obtained for the related ligands 1,4,7,10,13,16-hexaazacyclo-octadecane, 1,4,7,10,13,16,19-heptaazacyclohenicosane and 1,4,7,13-tetramethyl-1,4,7,10,13,16-hexaazacyclo-octadecane. Among these macrocycles L is a selective receptor for ATP binding.