The phenol-based macrocyclic ligands (L-2,L-3)(2-) and (L-2,L-4)(2-), derived from the [2:1:1] condensation of 2,6-diformyl-4-methylphenol, ethylenediamine, and 1,3-trimethylenediamine or 1,4-tetramethylenediamine, have a salen-like metal-binding site (salen = N,N'-ethylenedisalicylideneaminate) and a saltn- or salbn-like metal-binding site (salen = N,N'-trimethylenedisalicylideneaminate), salbn = N,N'-tetrameihylenedisalicylideneaminate sharing the phenolic moieties. They form the (mu-phenoxo)(2)(CoMII)-M-II complexes [CoMn(L-2,L-3)(AcO)]ClO4. DMF (1), [CoMn(L-2,L-4)(AcO)]ClO4 (2), [CoCo(L-2,L-3)(AcO)]ClO4 (3), [CoCo(L-2,L-4)(AcO)]ClO4 (4), [CoZn(L-2,L-3)(AcO)]ClO4 (5), and [CoZn(L-2,L-4)(AcO)]ClO4 (6). Complex 1 crystallizes in the monoclinic space group P2(1)/c, with a 10.027(3) Angstrom, b = 11.713(3) Angstrom, c = 26.821(9) Angstrom, beta = 93.85(2)degrees, V = 3142(1) Angstrom(3), and Z = 4. The Co and Mn ions are bridged by the two phenolic oxygens of the macrocycle and an acetate group in the syn-syn mode. The Co-II in the salen sire is of low-spin and assumes a square-pyramidal geometry with an acetate oxygen at the axial site. The Mn-II has a cis six-coordinate geometry with respect to the acetate oxygen and the DMF oxygen. The Mn is displaced 0.955 Angstrom from the basal N2O2 least-squares plane. [CoMn(L-2,L-4)(AcO)]ClO4. DMF (2') crystallizes in the monoclinic space group P2(1)/c, with a = 10.166(5) Angstrom, b = 11.934(4) Angstrom, c = 27.380(8) Angstrom, beta = 93.97(3)degrees, V = 3313(1) Angstrom(3), and Z = 4. It has a dinuclear core similar to that of 1, with square-pyramidal Co-II in the salen site and cis six-coordinate Mn-II in the salbn site. Complex 3 crystallizes in the triclinic space group P (1) over bar, 12.118(3) Angstrom, b = 12.156(2) Angstrom, c = 9.977(1) Angstrom, alpha = 112.49(1)degrees, beta = 99.22(2)degrees, gamma = 77.63(2)degrees, V = 1321.1(5) Angstrom(3), and Z = 2. Both Co-II ions in the salen and saltn sites assume a square-pyramidal geometry with a bridging acetate group in the syn-syn mode. The displacement of the Co in the saltn site, from the basal N2O2 least-squares plane toward the apical acetate oxygen, is 0.53 Angstrom. Complex 5 is found to be isostructural with 3. The complexes 1, 2, 4, 5, and 6 are reversibly oxygenated in DMF at 0 degrees C to afford a mu-peroxo dimer complex [{(CoMII)-M-III(L)(AcO)}(2)(O-2(2-))](2+). Complex 3 also forms such a mu-peroxo dimer complex but is irreversibly oxidized through an intramolecular-type mu-peroxo complex [(CoCoIII)-Co-III(L-2,L-3)(AcO) (O-2(2-))](+).