Synthesis, Structural Characterization, and Photochromic Behavior of a New Hybrid Diphosphomolybdate Compound

This is the authors' abstract. We don't add key points for this paper.

The integration of organic species with polyoxometalates leads to the formation of hybrid materials that benefit from the combined functionalities of both components. These organo-inorganic systems are of great interest due to their potential synergistic behavior. Developing straightforward and efficient synthetic approaches to design such materials combining the rigidity of the inorganic backbone and the tunability of organic units remains a key objective in the field of materials chemistry. In this work, we present a simple "one-pot" synthesis route for the compound (C₆H₂₀N₃)₂[P₂Mo₅O₂₃].1.5H₂O. Structural characterization was performed using single-crystal X-ray diffraction alongside infrared and UV-Visible spectroscopy. The compound crystallizes in the monoclinic system, space group P2₁/c, with the following unit cell parameters: a = 18.9626(2) Å, b = 10.8514(1) Å, c = 16.4933(1) Å, β = 107.37(1)°, and Z = 4. Its structure is based on a diphosphomolybdate anion [P₂Mo₅O₂₃]⁶⁻, neutralized by two organic cations (C₆H₂₀N₃)³⁺, and accompanied by 1.5 lattice water molecules. The three-dimensional arrangement is characterized by layered assemblies oriented along the a-axis, stabilized through extensive hydrogen bonding. These layers alternate between polyanionic clusters, organic moieties, and water molecules, forming a robust supramolecular network. Notably, this material displays photochromic behavior, suggesting its potential for applications in responsive optical systems.