Rare earth salicylates ligands

Salicylates.—In the course of his intramolecular energy transfer studies (p. 130) on europium chelates Weissman 630 prepared the 3-nitro and 5-nitro salicylate complexes. He was one of the first to demonstrate the phenomena of intramolecular energy transfer (IMET) from the coordinated ligands to the central rare earth ions giving characteristic fluorescence of the metal ions. However, no analytical data on these compounds are available. 

Formation constants of 3d metal ions with A-m-tolyl-p-substituted benzohydroxamic acids and of rare earths with thenoylhydroxamic acid have been determined. Formation constants of proton and metal complexes of iV-phenyl-2-thenoyl- and A-p-tolyl-2-thenoyl-hydroxamic acids have also been determined. In addition, study has been made of the mixed ligand complexes involving nicotine- and isonicotino-hydroxamic acids. A method of extraction and spectrophotometric determination of vanadium with chlorophenylmethylbenzohydroxamic acid has also been published. It may be mentioned that hydroxamic acids (in particular, the A-phenylbenzohydroxamic acid) have been widely used as analytical reagents for metal ions. Solvent extraction of titanium by benzo- or salicyl-hydroxamic acid in the presence of trioctylamine in the form of coloured complexes has been reported. A-w-Tolyl-p-methoxybenzohydroxamic acid has been used for extraction and spectrophotometric determination of Mo and W from hydrochloric acid media containing thiocyanate. 

These compounds have included the salicylate, anthianilate, glycolate and cinnamate ligand systems and the synthetic and stmctuial aspects of some of these rare earth complexes follow. 

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