With the established chemistry of bridged [(porphyrinate)Fe-III-X-Cu-II(ligand)](n+) [X = O2- (oxo), OH-(hydroxo), O-2(2-) (peroxo)] complexes, we investigated the effect of cobalt ion substitution for copper or copper and iron. Thus, in this report, the generation and characterization of new mu-oxo, mu-hydroxo, and mu-peroxo (mu-X) assemblies of [(porphyrinate)M-III-X-Co-II/III(TMPA)](n+) assemblies is described, where M = Fe-III or Co-III and TMPA = tris(2-pyridylmethyl)amine. The mu-oxo complex [(F8TPP)Fe-III-O-Co-II(TMPA)](+) (1, F8TPP = tetrakis(2,6-difluorphenyl)porphyrinate) was isolated by an acid-base self-assembly reaction of a 1:1 mixture of (F8TPP)Fe-III-OH and [Co-II(TMPA)(MeCN)](2+) upon addition of triethylamine. The crystal structure of 1 center dot 2C(4)H(10)O proved the presence of an unsupported Fe-O-Co moiety; > Fe-O-Co = 171.6 degrees and d(Fe center dot center dot center dot Co) = 3.58 A. Complex 1 was further characterized by UV-vis (lambda(max) = 437 (Soret) and 557 nm), H-1 NMR [delta 40.6 (pyrrole-H), 8.8 and 8.7 (m-phenyl-H), 8.0 (p-phenyl-H), 4.4 (PY-4H), 2.6 (PY-3H), 1.0 (PY-5H), -1.1 (PY-6H), and -2.7 (TMPA-CH2-) ppm], electrospray ionization (ESI) and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometric methods, Evans method NMR (mu(eff) = 3.1), and superconducting quantum interference device (SQUID) susceptometry (J = -114 cm(-1), S = 1). The mu-hydroxo analogue [(F8TPP)Fe-III-(OH)-Co-II(TMPA)](+) (2) [UV-vis lambda(max) = 567 nm; delta 78 ppm (pyrrole-H); Evans NMR mu(eff) = 3.7] was generated by addition of 1 equiv of triflic acid to 1. The protonation is completely reversible, and 1 is regenerated from 2 by addition of triethylamine. While (F8TPP)Fe-II/[Co-II(TMPA)(MeCN)](2+)/O-2 chemistry does not lead to a stable mu-peroxo species, a dicobalt mu-peroxo complex [(TPP)Co-III-(O-2(2-))-Co-III(TMPA)](2+) (< 3, TPP = meso-tetraphenylporphyrinate) forms from a reaction of O-2 with a 1:1 mixture of the Co-II precursor components at -80 degrees C [UV-vis lambda(max) = 435 (Soret), 548, and 583 (weak) nm; silent EPR spectrum; diamagnetic NMR spectrum]. The oxygenation/deoxygenation equilibrium is reversible; warming solutions of 3 releases similar to 1 equiv of O-2 and the reduced complexes are reformed.