Synthesis, Crystal Structure, Vibrational and Optical Properties of (Hdea)4(V7O19F)∙0.42H2O, an Original (V7O19F)4− Cluster Oxyfluoride

Synthesis, crystal structure, IR and Raman spectroscopies and optical analysis are reported for a new fluorovanadate with organic cations (Hdea)4(V7O19F)∙0.42H2O (dea: diethylamine). The title compound crystallizes in orthorhombic system, space group P212121, a = 11.486 (5) Å, b = 14.779 (5) Å, c = 23.243 (5) Å, Z = 4, V = 3,946 (2) Å3, R = 0.025 with 6,936 reflections. The atomic arrangement can be described as an alternation of inorganic and organic layers. The anionic layer is built up of original clusters (V7O19F)4− which are composed of three VO5F octahedra and four VO4 tetrahedra combined via shared edges and corners. The cohesion between the fluorovanadate groups, organic cations and water molecules is provided by a network hydrogen-bonding. The IR and Raman spectra exhibit characteristic bands of all groups present in the structure. The optical band gap is determined to be 2.5 eV by UV–Vis-T90+ diffuse reflectance spectra, which revealed the nature of semiconductor.