Synthesis, structure, electrochemistry, and magnetism of [(MnMnIII)-Mn-III], [(MnFeIII)-Fe-III] and [(FeFeIII)-Fe-III] cores: Generation of phenoxyl radical containing [(FeFeIII)-Fe-III] species

Neutral homo- and heterobinuclear complexes with the general formula [(tmta cn)M-A(salox)(3)M-B] where M-A (Mn-III or Fe-III) is facially coordinated t o the cyclic amine 1,4,7-trimethyl-1,4,7-triazacyclononane (tmtacn) and M-B (Mn-III or Fe-III) is coordinated to the azomethine nitrogens and phenolat e oxygens of the bridging ligand, salicylaldoxime, thus yielding MAN3O3 and MBN3O3 cores. The compounds were characterized by IR, UV/Vis, mass spectro metry, Mossbauer spectroscopy, electrochemistry, and variable-temperature ( 2-295 K) magnetic susceptibility measurements. The molecular structures of the compounds [(tmtacn)Fe-III(salox)(3)Fe-III] (3) and {(tmtacn)Fe-III (tBu Salox)(3)Fe-III} (4) were established by X-ray diffraction, Three oximate g roups -HC=N-O bridge the metal centers with Fe . . . Fe separations of 3.57 1(1) and 3.486(1) Angstrom for (3) and (4), respectively. Analysis of the s usceptibility data yields antiferromagnetic interactions between the metal centers for the complexes (FeFeIII)-Fe-III and Mn-III-Fe-III, but a ferroma gnetic interaction for (MnMnIII)-Mn-III. The electrochemistry of all comple xes was investigated in detail. For the complexes (FeFeIII)-Fe-III. (3) and (4) a series of reversible one-electron transfer waves leads to the format ion of the cations [Fe-2](1+/2+/3+) that are attributed to the generation o f salox-based phenoxyl radicals.