Mechanochemically synthesized crystalline luminescent 2D coordination polymers of La3+ and Ce3+, doped with Sm3+, Eu3+, Tb3+, and Dy3+: synthesis, crystal structures and luminescence

Abstract

The luminescence properties of two series of heteronuclear lanthanide-based coordination polymers were studied. The heteronuclear compounds were synthesized via mechanosynthesis routes. These series have the general chemical formula [Ln_1−xLn′_x(pzdc)(Hpzdc)(H₂O)₃]_n (Ln = La³⁺ or Ce³⁺, Ln′ = Sm³⁺, Eu³⁺, Tb³⁺, or Dy³⁺, x = 0.050, 0.075 or 0.100) where H₂pzdc stands for 2,3-pyrazinedicarboxylic acid (Hpzdc⁻ = mono-deprotonated and pzdc²⁻ = bis-deprotonated). The heteronuclear compounds that belong to each series are isostructural to a new two-dimensional La(III) coordination polymer and to an already reported homonuclear two-dimensional Ce(III) coordination polymer, [La(pzdc)(Hpzdc)(H₂O)₃]_n and [Ce(pzdc)(Hpzdc)(H₂O)₃]_n, respectively. These two crystal structures are isostructural as well. The La(III) and Ce(III) compounds have been synthesized via conventional heating and mechanosynthesis. The La(III) coordination polymer was structurally characterized by single crystal X-ray diffraction and was shown to consist of 2D sheets that construct a three-dimensional supramolecular architecture via non-covalent interactions i.e. hydrogen bonding. To find the optimal lanthanide-ion concentrations, the systems were doped with 5%, 7.5% or 10% of a spectroscopically active ion (Sm³⁺, Eu³⁺, Tb³⁺, or Dy³⁺) to investigate the luminescence properties.