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

A mixed-valence heterometallic nonanuclear [3 × 3] grid complex, [Cu I 2 Cu II 6 Fe III (L) 6 ](BF 4 ) 5 ·MeOH·9H 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)-1 H -pyrazol-3-yl]pyridine (H 2 L). 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 [Cu II 8 Fe III (L) 6 ](PF 6 ) 7 ·4MeOH·7H 2 O ( 1 2eOx ), the two-electron-reduced species [Cu I 4 Cu II 4 Fe III (L) 6 ](PF 6 ) 3 ·2H 2 O ( 1 2eRed ), and the three-electron-reduced species [Cu I 4 Cu II 4 Fe II (L) 6 ](PF 6 ) 2 ·5MeOH·H 2 O ( 1 3eRed ) were isolated electrochemically. The four redox isomers were characterized by single-crystal X-ray analysis, SQUID magnetometry, and Mössbauer spectroscopy.