PROPERTIES OF TRANSITION-METAL COMPLEXES WITH 15-MEMBERED, 16-MEMBERED AND 17-MEMBERED MACROCYCLES, DIOXOCYCLOPENTAAMINETRIACETIC ACIDS, INAQUEOUS-SOLUTIONS AND STRUCTURES OF THE LIGANDS IN THE SOLID-STATE

Formation constants, UV-Vis spectra and EPR spectra have been obtained for Mn2+, Co2+, Ni2+, Cu2+ and Zn2+ complexes formed in aqueous solut ions with 15-, 16- and 17-membered macrocycles, which are 4,7,10,13-pe ntaaza-1,4,7-cyclopentadecanetriacetic acid (abbreviated as (15dtpaen) H-3), ,10,14-pentaaza-1,4,7-cyclohexadecanetriaceticacid ((16dtpapn)H -3) and 9,16-dioxo-1,4,7,10,15-pentaaza-1 ,4,7-cycloheptadecanetriacet icacid ((17dtpabn)H-3), respectively. The ligands (16dtpapn)H-3 and (1 7dtpabn)H-3 were characterized by single crystal X-ray analyses: (16dt papn)H-3, C17H29N5O8 . 3H(2)O, crystallized in the triclinic space gro up <P(1)over bar> with a = 9.795(2), b = 10.743(2), c = 11.635(2) Angs trom, alpha = 75.590(2), beta = 84.832(2), gamma = 77.214(2)degrees an d Z = 2; (17dtpabn) H-3,C18H31N5O8 . 2H(2)O, crystallized in the tricl inic space group <P(1)over bar> with a = 10.075(2), b = 10.524(1), c = 11.705(1) Angstrom, alpha = 78.12(1), beta = 71.57(1), gamma = 83.56( 1)degrees and Z = 2. In (16dtpapn) H-3, the central carboxylate oxygen and two terminal amine nitrogens are protonated; in (17dtpabn) H-3 tw o terminal carboxylate oxygens and the central amine nitrogen are prot onated. The molecular conformation of(l7dtpabn) H, is preorganized for complex formation, whereas (16dtpapn)H-3 is not preorganized. These s tructural features of the ligands are reflected in the pH dependence o f the electronic and EPR spectra of the metal chelates.