Syntheses, crystal structures and luminescent properties of two novel lanthanide/4-pya complexes: [Ln(4-pya)3(H2O)2]2 (Ln = Eu, La; 4-pya = trans-4-pyridylacrylate)

Reactions of Ln2O3 and trans-4-pyridylacrylic acid (4-Hpya) in EtOH/H2O or MeOH/H2O produced two new lanthanide/4-pya complexes [Ln(4-pya)3(H2O)2]2 (1: Ln = Eu; 2: Ln = La) in low yields. However, reactions of LnCl3 · 6H2O with 4-Hpya/aqueous ammonia in EtOH/H2O or MeOH/H2O gave rise to 1 or 2 in higher yields. Both compounds were structurally characterized by elemental analysis, IR spectroscopy and X-ray analysis. Compounds 1 · 2EtOH · 2H2O and 2 · 2MeOH · 2H2O were confirmed to possess one-dimensional polymeric chain structures. In the structure of 1, each Eu(III) adopts a monocapped square-antiprism coordination geometry and each dimer [Eu(4-pya)3(H2O)2]2 within the chain is interconnected by two pairs of different bridging 4-pya ligands. On the other hand, each La(III) of 2 takes a bicapped square-antiprism coordination geometry and each dimer [La(4-pya)3(H2O)2]2 within the chain is linked by two pairs of tridentate bridging 4-pya ligands. The luminescent properties of 1 and 2 in the solid state were investigated.