Structure and electrochemical properties of (μ-O)2Mn2(iii,iii) and (μ-O)2Mn2(iii,iv) complexes supported by pyridine-, quinoline-, isoquinoline- and quinoxaline-based tetranitrogen ligands

Seven new bis(μ-oxo)dimanganese complexes with Mn2(iii,iii) or Mn2(iii,iv) oxidation states were prepared using quinoline- and isoquinoline-based tetraamine ligands. The structures of the ligands include ethylenediamine, trans-1,2-cyclohexanediamine and tripodal amine, bearing two or three nitrogen-containing heteroaromatics. Regardless of the skeleton and number of aliphatic nitrogen atoms in the ligands, quinoline complexes stabilize the Mn2(iii,iii) oxidation state, whereas, isoquinoline ligands afford Mn2(iii,iv) complexes. A systematic comparison of the differences in structural parameters and redox potentials of a total of 14 complexes with a (μ-O)2Mn2 diamond core, which includes corresponding pyridine and quinoxaline derivatives as supporting ligands, highlights the distinct deviation of quinoline and tripodal amine motifs in this ligand series.