Four Redox Isomers of a [3 x 3] Copper-Iron Heterometal Grid

A mixed-valence heterometallic nonanuclear [3 x 3] grid complex, [(Cu2Cu6FeIII)-Cu-I-Fe-II(L)(6)](BF4)(5)MeOH9H(2)O (1; MeOH = methanol), was synthesized by a one-pot reaction of copper and iron ions with multidentate ligand 2,6-bis[5-(2-pyridinyl)-1H-pyrazol-3-yl]pyridine (H2L). 1 showed five quasi-reversible one-electron redox processes centered at +0.74, +0.60, +0.39, +0.27, and -0.13 V versus SCE, assignable to four Cu-I/Cu-II processes and one Fe-II/Fe-III couple, respectively. The two-electron-oxidized species [(Cu8FeIII)-Fe-II(L)(6)](PF6)(7)4MeOH7H(2)O (1(2eOx)), the two-electron-reduced species [(Cu4Cu4FeIII)-Cu-I-Fe-II(L)(6)](PF6)(3)2H(2)O (1(2eRed)), and the three-electron-reduced species [(Cu4Cu4FeII)-Cu-I-Fe-II(L)(6)](PF6)(2)5MeOHH2O (1(3eRed)) were isolated electrochemically. The four redox isomers were characterized by single-crystal X-ray analysis, SQUID magnetometry, and M & ouml;ssbauer spectroscopy.