Uncommon coordination modes of a potential heptadentate aminophenol donor

This work describes the synthesis, characterization and reactivity towards Ho^III of a potential heptadentate N₄O₃ aminophenol donor. The crystal structure of the [Ho(1,1,4-H₃L)(1,1,4-H₆L)] complex (1,1,4-H₆L = 6,6'-(2-(5-bromo-2-hydroxy -3-nitrobenzyl)-2,5,8,11-tetraazadodecane-1,12-diyl)bis(4-bromo-2-nitrophenol)) shows that the holmium atom binds two aminophenol ligands, one acting as trianionic hexadentate, and the other one as neutral monodentate. As far as we know, both coordination modes of the aminophenol are hitherto unknown for this kind of scarcely reported ligand. This leads to a coordination number of 7 for the Ho^III ion, which is in a capped trigonal prism environment.