Crystal Structures and Luminescence Properties of [Ln(NTA)2·H2O]3-Complexes (Ln = Sm3+, Eu+3, Gd3+, Tb3+, Ho3+, and NTA = Nitrilotriacetate)

Abstract

Crystal structures of lanthanide complexes with NTA (NTA = nitrilotriacetate) are reported. The complexes of <TEX>$[Ln(NTA)_2{\cdot}H_2O]^{3-}$</TEX> (Ln = Sm, Eu, Gd, Tb and Ho) crystallize in the orthorhombic space group Pccn. In the structures, the trivalent lanthanide ions are completely encapsulated via coordination to the two nitrogen atoms and the six carboxylate oxygen atoms of the two NTA ligands, and one water oxygen atoms. The complexes form a slightly distorted capped-square-antiprism polyhedron. Of the complexes, <TEX>$[Eu(NTA)_2{\codt}H_2O]^{3-}$</TEX>,\;[Tb(NTA)_2{\cdot}H_2O]^{3-}\;and\;[Dy(NTA)_2{\cdot}H_2O]^{3-}$</TEX> excited at the 325 He-Cd line produce very characteristic luminescence features, arising mostly from the f <TEX>${\to}$</TEX> f transitions. The absolute quantum yields of these complexes are determined at room temperature. Surprisingly, the <TEX>$[Dy(NTA)_2{\cdot}H_2O]^{3-}$</TEX> complex is more luminescent than the <TEX>$[Eu(NTA)_2{\cdot}H_2O]^{3-}\;and\;[Tb(NTA)_2{\cdot}H_2O]^{3-}$</TEX> complexes.