A new paradigmatic lanthanide coordination chemistry: Assembling lanthanide-hydroxo clusters under physiological or higher-pH conditions

High-nuclearity lanthanide-hydroxo complexes were prepared via limited hydrolysis of lanthanides using α-amino acids or EDTA as supporting ligands. These novel substances, synthesized under physiological or even higher-pH conditions, exist as tetranuclear cuboid [Ln ₄(μ ₃-OH ₄] ⁸⁺ core-containing clusters. With appropriate halide templates, "wheel-like" supramolecular structures composed of four or five vertex-sharing [Ln ₄ (μ ₃-OH) ₄] ⁸⁺ units are formed. The face-capped octahedral [Ln ₆/μ ₆-O)(μ ₃-OH) ₈] ⁸⁺ cluster centering on an interstitial μ ₆-O ligand is another stable form of lanthanide-hydroxo complexes and can be self-assembled via direct hydrolysis of lanthanide nitrates and perchlorates. The significant influence of pH conditions on lanthanide coordination chemistry is further illustrated by a new paradigmatic lanthanide-EDTA chemistry, wherein unprecedented multinuclear Ln-EDTA cluster complexes are realized.