TRANSITION-METAL COMPLEXES OF 12-MEMBERED AND 13-MEMBERED FUNCTIONALIZED MACROCYCLES, DIOXOTETRAAZACYCLOALKANEDIACETATES

Formation constants of Mn2+, Co2+, Ni2+, CU2+, and Zn2+ complexes form ed in aqueous solutions with 12-membered and 13-membered macrocycles h ave been determined, and the solution electronic spectra have been stu died. The 12-membered macrocycle, abbreviated as (12edtaen)H-2, is -di oxo-1,4,7,10-tetraaza-4,7-cyclododecanediacetic acid and the 13-member ed macrocycle, abbreviated as (13edtapn)H-2, is dioxo-1,4,7,10-tetraaz a-4,7-cyclotridecanediacetic acid. The structures of [Zn(C12H18N4O6)]. 4H(2)O and [Mn(C13H20N4O6)(H2O)](2) . 7H(2)O have been determined by single-crystal X-ray analyses. The zinc complex crystallized in the mo noclinic space group P2(1)/n with a = 10.205(2) Angstrom, b = 9.599(2) Angstrom, c = 19.431(3) Angstrom, beta = 100.268 (2)degrees, and Z = 4. The coordination geometry around the zinc atom is distorted octahed ral with five donor atoms (two amine nitrogen, an amide oxygen, and tw o acetate oxygen atoms) from one ligand molecule and an acetate oxygen atom from a neighboring zinc chelate. The zinc atoms are linked by Zn -O-C-O-Zn bonds and form a one-dimensional array. The manganese comple x crystallized in the orthorhombic space group Peen with a = 16.325(1) Angstrom, b = 17.468(1) Angstrom, c = 15.144(1) Angstrom, and Z = 4. The coordination geometry around the manganese atom is a highly distor ted trigonal prism with five donor atoms from a ligand molecule and an oxygen atom from a water molecule. The formation constants of the ML species of Ni2+ and CU2+ With (12edtaen)(2-) are significantly higher than those of the corresponding complexes with (13edtapn)(2-). The MLH (-2) species of Co2+, Ni2+, and CU2+ formed with (13edtapn)(2-) in the basic region have greater formation constants than the corresponding MLH(-1) species. The solution electronic spectra of the MLH(-2) specie s of these complexes are quite different from those of the correspondi ng ML species, indicating that conversion of coordination geometry occ urs as a result of deprotonation of amide nitrogen atoms. This convers ion has been confirmed by an electron spin echo envelope modulation ex periment for the CU2+ complex. No significant spectral changes are obs erved with the M(12edtaen) complexes. In these complexes the mixed-lig and complexes, M(12edtaen)(OH)(n) (n = 1 or 2), are formed in the basi c region, and the complexes with n = 2 are much less stable than the c orresponding complexes with n = 1. These large differences in the prop erties of the metal complexes of the two macrocyclic ligands are cause d by a difference of only one -CH2- group in the ligand ring system.