A Systematic Look at Structural Diversity of Metal Phosphonates

Herein, we report the synthesis of three new copper phosphonate frameworks using a tetrahedral-shaped organic building block, methane tetra-p-phenylphosphonic acid (H₈-MTPPA), and three different N-ancillary ligands terpyridine (terpy), 2,2’-bipyridine (2,2’-bpy), phenanthroline (phen) to optimize the ligand binding modes on copper coordination sphere to generate molecular secondary building units (SBUs) in metal organophosphonates. We report the crystal structures of rod-shaped one-dimensional zig-zag chain structure, [{Cu(terpy)}(H₆-MTPPA)(H₂O)]⋅2H₂O, three-dimensional framework, [{Cu₅(2,2’-bpy)₂}(H₂-MTPPA)(H₄-MTPPA)], and one-dimensional structure [{Cu₂(phen)₂}(H₄-MTPPA)]⋅4H₂O. Magnetic analysis of three-dimensional copper phosphonate framework, namely [{Cu₅(2,2’-bpy)₂}(H₂-MTPPA)(H₄-MTPPA)], showed paramagnetic behavior. Crystal structures were characterized by single crystal X-ray diffraction, FT-IR, and thermogravimetric analysis (TGA).