Structural Characterization and Redox Activity of a Uranyl Dimer and Transition-Metal Complexes of a Tetradentate BIAN Ligand

The synthesis and characterization of a new ligand system combining the redox-active backbone of Ar-BIANs (N,N′-bis­[(aryl)­imino]­acenaphthenes) and a mixed-donor O–N–N–O salen-type binding pocket is reported. Complexes of Co2+, Ni2+, and UO22+ were prepared and characterized through single-crystal X-ray diffraction and electrochemical studies. The Ni2+ and Co2+ complexes have been used as references against which to compare the unique behaviors exhibited by the uranyl (UO22+) complex, as the latter forms two distinct solid-state structures with unusual oxo contacts to CH2Cl2 and CHCl3 and displays a rich electrochemical profile that indicates a wide range of accessible metal oxidation states through the formation of mixed-valent U­(VI)/U­(V) and U­(V)/U­(IV) species in solution.