Europium(II) complexes with nitrilotriacetic acid (NTA)

Abstract

The article presents two complexes of divalent Eu with nitrilotriacetic acid. The first of them, polymeric trisaqua(nitrilotriacetato)sesquieuropium hydrate, [(C 6H 6NO 6)(H 2O) 3Eu 3/2]·H 2O, precipitates during electrochemical reduction from acidic solution. There are two independent Eu 2+ cations: one is 8-coordinate (six carboxylic oxygen atoms and two water molecules), whereas the other is nine-coordinate (four carboxylic oxygen atoms, four water molecules, and a nitrogen atom). The other complex, hexacaesium bis(nitrilotriacetato)europate(II) dichloride tetrahydrate, Cs 6[(C 6H 6NO 6) 2Eu]Cl 2·4H 2O, obtained in basic environment, is monomeric. Europium is eight-coordinate (six carboxylic oxygen and two nitrogen atoms) and its environment has an approximate S 6 symmetry. The latter compound displays very weak luminescence with maximum at 483 nm at 77 K.