Synthesis, characterization and luminescence properties of europium(III) and terbium(III) complexes with 2-pyrazinecarboxylic acid -: Crystal structure of [Eu(pyca)3(H2O)2]•6H2O

New europium(III) and terbium(III) complexes with 2-pyrazinecarboxylic acid (Hpyca) were synthesized and characterized by elemental, IR and photoluminescence analyses. The single crystal X-ray structure of [Eu(pyca)(3)(H2O)(2)].6H(2)O was determined. Europium(III) atom is nine-coordinate surrounded by three O- and N-atoms from three pyca(-) ligands, one bridging carboxylate oxygen atom from the neighboring molecule, and two oxygen atoms from two water molecules. The crystal structure of [Eu(pyca)(3)(H2O)(2)].6H(2)O can be described as three dimensional network, in which a neighboring zigzag [Eu(pyca)(3)(H2O)(2)](infinity) chains are further connected by pi-pi interactions of pyrazine rings. A comparison of the photoluminescent spectra of Ln(pyca)(3) and Ln(bz)(3) (Ln: Eu, Tb; Hbz: benzoic acid) revealed that the insertion of two nitrogen atoms into the benzene ring of benzoic acid strongly influences on the intensity and relative quantum efficiency of the corresponding lanthanide complexes. (C) 2003 Elsevier B.V. All rights reserved.