MANGANESE(II) AND GADOLINIUM(III) COMPLEXES WITH NEW 13-MEMBERED AND 16-MEMBERED DIOXOPOLYAZACYCLOALKANES HAVING PENDANT HYDROXY AND CARBOXYMETHYL GROUPS

New 13-membered and 16-membered functionalized macrocycles, dioxopolya zacycloalkanes with pendant hydroxy and carboxymethyl groups, have bee n synthesized: the 13-membered macrocycle is 12-hydroxy-2,9-dioxo-1,4, 7,- 10-tetraaza-4,7-cyclotridecanediacetic acid [abbreviated as (13edt apnOH)H-2] and the 16-membered macrocycle is 4,7,10,13-pentaaza-4,7,10 -cyclohexadecanetriacetic acid [(16dtpapnOH)H-3]. The resulting macroc ycles have been characterized by H-1 NMR at different pD values, and t he protonation sites and the proton populations have been determined f or each protonation step. Nonionic Mn2+ and Gd3+ complexes with these ligands, [Mn(13edtapnOH)(H2O)]. 3H(2)O and [Gd(16dtpapnOH)(H2O)]. 3H(2 )O, have been characterized by single-crystal X-ray analyses. The Mn2 complex crystallized in the triclinic space group <P(1)over bar> with a = 11.453-(1) Angstrom, b = 12.432(1) Angstrom, c = 14.432(2) Angstr om, alpha = 77.39(1)degrees, beta = 76.24(1)degrees, gamma = 88.50(1)d egrees, and Z = 4. The unit cell contains two types of metal chelate m olecules: one has a six-coordination geometry described by a quasi-tri gonal prism and the other has a seven-coordination geometry described by a distorted capped trigonal prism. The formation of the two types o f Mn2+ chelate molecules arises from interaction between an OH oxygen and an amide nitrogen in a coordinated ligand molecule. The Gd3+ compl ex crystallized in the monoclinic space group Pc with a = 8.405(2) Ang strom, b = 9.688(3) Angstrom, c = 16.392(4) Angstrom, beta = 109.117(3 )degrees, and Z = 2. The coordination geometry of the Gd3+ complex is a tricapped trigonal prism. The electron paramagnetic resonance hyperf ine structure of the Mn2+ complex in a glass matrix showed the so-call ed forbidden-transition (Delta m(I) = +/- 1) lines at intermediate fie lds between the allowed-transition (Delta m(I) = 0) lines. The NMR T-1 and T-2 relaxivities of the Gd3+ complex in 90% D2O were determined t o be r(1) = 3.45 s(-1) mM(-1) acid r(2) = 4.4 s(-1) mM(-1) at 250 MHz. The H-1 NMR spectra of the free ligands show that the introduction of an OH group increases the rigidity of the ring systems, owing to inte raction between the hydroxy and amide groups. This interaction is resp onsible in part for the structural and solution properties of the meta l chelates.