Ionothermal Synthesis and phase transformation of organic-inorganic hybrid neutral zincophosphate cluster [Zn(HPO₄)(H₂PO₄)][C₆H₁₀N₃O₂]

Ionothermal synthesis was used to prepare a novel amino acid containing hybrid zincophosphate monomer, [Zn(HPO₄)(H₂PO₄)][C₆H₁₀N₃O₂](denoted as ZnPO-CJ58). The inorganic framework of [Zn(HPO₄)(H₂PO₄)]· [C₆H₁₀N₃O₂] consists of 4-membered rings formed by ZnO₃O_His and PO₂(OH)₂ tetrahedra. The HPO₄ and amino acid moieties hang on the Zn center. Such a framework is stabilized by extensive multipoint hydrogen bonds involving the phosphate units and histidine molecules to form a pseudo-3D supramolecular structure. It is noteworthy that ZnPO-CJ58 is the first zinc phosphate cluster with amino acid acting as the ligand. It exhibits photoluminescence excited at a wavelength of 220 nm. Interestingly, ZnPO-CJ58 can transform into a layered structure (C₆H₁₀N₃O₂)Zn₂· (HPO₄)(PO₄)·H₂O(ZnPO-CJ36) through further reacting with water or zinc acetate dihydrate in water at 85 °C for 1 h. This work will be helpful for the synthesis of crystalline inorganic-organic hybrid materials with biofunctional molecules.