Synthesis and ligational properties of a new tetra-azamacrocycle containing an anisolic function

The synthesis and characterization of the new tetra-azamacrocycle 1,4,7,10- tetraaza[12]-(2,6)anisolephane (L) are reported. The stepwise basicity cons tants were determined using potentiometric (0.15 mol dm(-3) NMe4Cl, 298 +/- 0.1 K) and NMR (H-1 and C-13) techniques. L behaves as a tetraprotic base: log K-1 = 9.62; log K-2 = 9.03; log K-3 = 5.44; log K-4 = 1.9. NMR experim ents allowed the determination of the protonation sequence. The influence o f the anisolic group inside the macrocyclic cavity upon the basicity behavi our is discussed. The equilibrium constants of the species formed by L with Co(II), Cu(II), Zn(II), Cd(II) and Pb(II) are reported and discussed. The formation constants for the oxygenated species [CoLO2](2+), [CoLHO2](3+) an d [CoL(OH)O-2](+) are: log K = 7.6(1), 15.8(1) and -1.3(1), respectively. ( C) 2000 Elsevier Science B.V. All rights reserved.