Synthesis, characterization, and crystal structure of a 2-D metal diphosphonate: Cu₃(H₂O)₂[HO₃PCH₂N(CH₃)CH₂PO₃]₂ · 2H₂O

Abstract

Hydrothermal reaction of N-methyl-iminobis(methylenephosphonic acid), CH₃N(CH₂PO₃H₂)₂, (H₄L) with copper(II) acetate afforded a new layered Cu(II) amino diphosphonate, Cu₃(H₂O)₂(HL)₂ · 2H₂O (1). Compound 1 was studied by IR spectroscopy, TGA/DTA data, and X-ray diffraction (XRD) techniques. The XRD patterns are the same for the hydrated and the dehydrated complexes. A single-crystal X-ray crystallographic determination reveals copper in two different coordination environments. Cu1 has a distorted elongated tetragonal octahedral geometry, whereas Cu2 has a square-pyramidal distorted geometry. The HL trianion is a pentadentate ligand with a deprotonated nitrogen atom and two oxygen atoms of each phosphonate binding to copper. Hydrogen bonds between lattice water molecules in interlayer spaces and the non-coordinated phosphonate oxygen atoms as well as water ligands leads to a 3-D supramolecular network structure.

Keywords:

• Copper
• Diphosphonate
• Crystal structure
• Hydrothermal synthesis

Acknowledgments

We thank the Research Council of Tarbiat Modares University for the financial support of this work.