Syntheses, crystal structures, thermal stabilities, magnetism and luminescence of two 3D metal phosphonates

Abstract

Hydrothermal reactions of Zn^II or Cu^II ion with 1-hydroxyl-2-(3-pyridyl)ethylidene-1,1-diphosphonic acid (H₄L) afforded two metal phosphonates, namely, [Zn₂(L)(H₂O)] (1) and [Cu₄(L)₂ (H₂O)₄]·(H₂O)_1.25 (2). In 1, [ZnO₃N], [ZnO₄] and [PO₃C] tetrahedra are connected through corner-sharings to form a 3D framework with a 14MR ellipsoid-like channel. In 2, the [PO₃C] tetrahedron also shares corners with a copper square-pyramid ([CuO₄N], [CuO₅]) into a hybrid layer, which is further pillared by L⁴⁻ anion into a 3D neutral framework. Solid 1 is thermally stable up to 250 °C under an air atmosphere and displays UV luminescence. More interestingly, the dehydrated phase of 1 is selective and reversible for sensing of nitrobenzene. And the magnetic property of 2 has also been studied.