Structure and luminescent properties of Nd(III) and Tb(III) coordination polymers with 2,4,6-pyridinetricarboxylate

Two lanthanide coordination polymers (CP) of Nd(III) and Tb(III) with 2,4,6-pyridinetricarboxylate ligands were synthesized by reacting Nd(III) or Tb(III) chlorides with 2,4,6-pyridinetricarboxylic acid (H₃ptc) by hydrothermal method at 180 °C. Their chemical formulas were {[Nd(ptc)(H₂O)₂]·H₂O}_n (CP-1) and {[Tb(ptc)(H₂O)₃]·H₂O}_n (CP-2). Two compounds were characterized by IR spectra and element analyses. The crystal structures were determined by X-ray single crystal diffraction. CP-1 formed three-dimensional (3D) structure by the connections of coordination bonds between Nd(III) and ptc ligands and CP-2 formed two-dimensional (2D) layered structure. They could produce the characteristic f-f transition luminescence of Nd(III) or Tb(III) ion with the excitations of UV-rays. The lifetime for ⁵D₄ excited state of Tb(III) in CP-2 was 741 μs. And the absolute quantum yield of photoluminescence for CP-2 can reach 60% (λ_ex = 295 nm).