SYNTHESIS, CRYSTAL-STRUCTURE, AND POTENTIOMETRY OF PRIDINE-CONTAINING TETRAAZA MACROCYCLIC LIGANDS WITH ACETATE PENDANT ARMS

Tetraazamacrocycles containing the pyridine moiety as part of the cyclic backbone and acetate pendant arms were prepared. The resulting products were characterized by high resolution NMR (H-1 and C-13) spectroscopy and single-crystal X-ray diffraction. Single-crystal X-ray diffraction data were obtained for the following compounds: py[12]aneN4 . HCl, C11H19N4Cl, orthorhombic Pnma (No. 62), a = 10.304(6) Angstrom, b = 9,160(2) Angstrom, c = 13.552(2) degrees, Z = 4, Mo K alpha, lambda = 0.710 69, R = 0.037, R(w) = 0.036; and BP2A . 2HCl . 3H(2)O, C18H22NO4Cl(2) . 3H(2)O, triclinic P (1) over bar (No. 2), a = 10.201(0) Angstrom, b = 13.267(3) Angstrom, c 8.612(6) alpha = 97.676(2)degrees, beta = 105.821(0)degrees, lambda = 86.363(7)degrees, Z = 2, Mo K alpha, lambda = 0.710 69, R = 0.039, R(w) = 0.038. In addition, protonation constants (log KHnL) and metal ion stability constants (log K-ML) for BP2A (log K-H1-4L = 9.57, 5.99, 2.59, 2.22; log K-MgL = 8.9; log K-CaL = 10 0; log K-GdL = 14.5) and PC2A (log K-H1-5L = 12.5, 5.75, 3.28, 2.38, similar to 1; log K-MgL = 8.4, log K-CaL = 10.0, log K-GdL = 16.6) were determined using potentiometric and NMR pH titrations. These values agree well with previously reported literature values for analogous ligand systems.