Heterocycle-lanthanide complexes, anion

Anion Recognition with Designed Heterocycle-Lanthanide Complexes... 

Heterocycle-Lanthanide Complexes for Anion Recognition and Sensing... 

Several heterocycle-lanthanide complexes provided attractive, imaginative, and suggestive approaches to anion sensing, in which Ugand architecture based on heterocyclic chemistry played important roles. Cyclen-lanthanide complexes have several advantages of facile design and systematic synthe-... 

In the synthesis of anionic amido-A -heterocyclic carbene complexes of lanthanides (22, Ln = Sm, Y N = (TMS)2N)) from the bridged imidazolium complex 20 via carbene 21, a typical increase in the length of the C-N bond and a decrease in the N-C-N angle were observed going from 20 to 21 <2003AGE5981>. The Sm-Ccarbene distance of 2.588(2) A is the shortest recorded compared to those reported for monodentate Sm-NHC complexes (2.62-2.83 A). 

Lanthanide complexes containing anionic amido iV-heterocyclic carbenes as ligands have been synthesized as illustrated in Scheme 24.162,162a... 

Several types of heterocyclic ligands were reported to form luminescent lanthanide complexes exhibiting anion-selective responses in non-aqueous me-... 

Complexes of picolinamide with lanthanide perchlorates, nitrates, and isothiocyanates have been isolated by Condorelli et al. (59). All these complexes show changes in the stoichiometry on going from La(III) to Lu(III). The ligand acts as bi-dentate with the oxygen of the amide group as well as the heterocyclic nitrogen coordinating to the metal (Structure I). While the anions in the perchlorate complexes are not coordinated to lanthanide ions, those in the nitrate and isothiocyanate complexes are coordinated. 

Arnold, P.L., Mungur, S.A., and Blake, A.J. (2003) Anionic amido N-heterocyclic carbenes synthesis of covalently tethered lanthanide-carbene complexes. Angewandte Chemie International Edition, 42, 5981. 

N-heterocyclic ligands have particularly complex behavior. In addition to coordinating to the metal, N-heterocycles can be protonated and act as counterions to anionic metal complexes. The polar, aromatic ring systems of these ligands can also give rise to a number of noncovalent interactions. As extractants, N-heterocycles such as bis(triazine) pincer ligands are an important class of extractants in actinide-lanthanide separations [57]. 1- and 2-methylimidazole have also been studied as extractants for lanthanides into ILs and show promise for intra-group separations [58]. 

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