Clusters lanthanide amino acid complexes

The above discussion suggests that the identity of the lanthanide amino acid complexes, more specifically, the structure of the core motif, is dependent more on the nature of the ligands than on that of the metal ions. With the assistance of small-molecule entities, cluster-type complexes with amino acid ligands with unprecedented structures may be realized. ... 

Amino acid is one of the most important biological ligands. Researches on the coordination of metal-amino acid complexes will help us better understand the complicated behavior of the active site in a metal enzyme. Up to now many Ln-amino acid complexes [50] and 1 1 or 1 2 transition metal-amino acid complexes [51] with the structural motifs of mononuclear entity or chain have been synthesized. Recently, a series of polynuclear lanthanide clusters with amino acid as a ligand were reported (most of them display a Ln404-cubane structural motif) [52]. It is also well known that amino acids are useful ligands for the construction of polynuclear copper clusters [53-56], Several studies on polynuclear transition metal clusters with amino acids as ligands, such as [C03] [57,58], [Co2Pt2] [59], [Zn6] [60], and [Fe ] [61] were also reported. 

Wang, R., Liu, H., Carducci, M.D., Jin, T, Zheng, C., and Zheng, Z. (2001) Lanthanide coord with a-amino acids under near physiological pH conditions polymetallic complexes containing the cubane-like [Ln (P3-0H)6] cluster core. Inorganic Chemistry, 40, 2743-2750. 

In view of the structural and functional relationship between amino acids and polyaminopolycarboxylic acids, the coordination of some lanthanide ions (La, Pr, Er) with ethylenediaminetetraacetate (EDTA) has also been examined under much higher pH conditions. The formation of lanthanide-hydroxo complexes formulated as K2R(0H)EDTA 4H20 was reported as early as in 1955 (Djordjevic and Vuletic, 1980), but it is not until recent studies that the first crystal structure of a lanthanide-EDTA hydroxo species was reported. Efforts in this field were also stimulated by the recognition that the R(OH2)s array present in previously known mononuclear EDTA complexes is dimensionally close to the R(/is-0H)3 fragment of [R4(/i3-OH)4] + clusters and by the desire to understand the mechanism of formation of the clusters. A proposal for the latter is outlined in Figure 90. 

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