Syntheses, crystal structures, thermal stabilities and luminescence of two metal phosphonates

Abstract

Hydrothermal reactions of Zn(II) or Pb(II) ions with 4-pyridyl-CH₂N(CH₂COOH)(CH₂PO₃H₂) (H₃L) afforded two metal phosphonates, namely, [Zn₃(L)₂]·2H₂O (1) and [Pb₃(L)₂(H₂O)₂]·H₂O (2). Compound 1 is a 3D pillared framework in which [ZnO₄] tetrahedra and [ZnO₃N₂] trigonal-bipyramids are connected by L³⁻ anions with heptadentate modes. In 2, L³⁻ anions exhibit pentadentate modes to combine Pb(II) ions into a complicated 2D hybrid layer, resulting in the non-coordinated pyridine rings being sandwiched between the layers. Solid 1 is thermally stable up to 350 °C under an air atmosphere and displays bright purple–blue luminescence, and the luminescent intensity of the hydrated solid 1 can be weakened by nitrobenzene.