Luminescence properties and crystal structure of europium complexes with phenoxyacetic acid and 2,4,6-tri(2-pyridyl)-s-triazine

Using anion ligand phenoxyacetic acid (HPOA) and neutral ligand 2,4,6-tri(2-pyridyl)-s-triazine (TPTZ), two complexes Eu₂(TPTZ)₂(POA)₆·6H₂O and EuY(TPTZ)₂(POA)₆·6H₂O have been synthesized and one crystal EuY(TPTZ)₂(POA)₆·2CH₃OH has been obtained. These complexes are characterized by elemental analysis, ICP-AES, IR and UV absorption spectroscopy. The luminescence spectra, luminescence lifetimes and emission quantum efficiencies of the complexes have been studied. The results show that the complex EuY(TPTZ)₂(POA)₆·6H₂O exhibits stronger luminescence intensity, longer luminescent lifetime and higher emission quantum efficiency than Eu₂(TPTZ)₂(POA)₆·6H₂O. The single-crystal X-ray diffraction of EuY(TPTZ)₂(POA)₆·2CH₃OH reveals that the crystal is heteronuclear and crystallizes in the triclinic space group P-1 with following unit cell parameters a=12.2411(10) Å, b=13.2294(11) Å, c=13.5232(11) Å, α=74.8596(13)°, β=82.9593(16)°, γ=87.1641(14)°, and V=2097.7(3) ų. Each metal ion coordinates with three nitrogen atoms of one TPTZ and seven oxygen atoms of three POA⁻ ions. And there exist two coordination forms between POA⁻ and metal ions in the crystal. One is chelating bidentate, the other is the single-atom bridge. - Highlights: • One Eu/Y heteronuclear crystal and two complexes with HPOA and TPTZ were prepared. • Each metal ion in the crystal coordinates with three nitrogen and seven oxygen atoms. • The two complexes exhibit strong luminescence emissions. • The heteronuclear complex shows better luminescent properties than the homonuclear one. • The structure of the crystal and the sensitization mechanism are deeply discussed