A holmium complex of a macrocyclic ligand (DOTA) and its isostructural europium analogue

The holmium and europium complexes of the tetraanion of 1,4,7,10-tetraazacy clododecane-1,4,7,10-tetraacetic acid (H(4)DOTA), namely, sodium aqua(1,4,7 , 10-tetraazacyclododecane-1,4,7, 10-tetraacetato)holmium(III) tetrahydrate , Na[Ho(C16H24N4O8)(H2O)]. 4H(2)O, and sodium aqua(1,4,7,10-tetraazacyclodo decane-1,4,7,10-tetraacetato)europium(III) tetrahydrate, Na[Eu(C16H24N4O8)( H2O)]. 4H(2)O, show nine-coordination around the metal ion, with a square a ntiprismatic coordination geometry involving four N- and four O-donor atoms of the DOTA ligand, and a coordinated water molecule in a capping position .