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 - 2 NEW MACROCYCLIC RECEPTORS FOR ATP BINDING - SYNTHESIS, SOLUTION EQUILIBRIA AND THE CRYSTAL-STRUCTURE OF (H(4)L)(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. The crystal structure of the compound (H(4)L)(ClO4)(4) [space group P2(1)/c, a = 9.257(4), b = 8.600(2), c = 17.990(10) Angstrom, beta = 101.74(4)degrees, V = 1402(1) Angstrom(3), Z = 2] shows that the four charged ammonium groups point inside the macrocyclic cavity.