Crystal structure and spectroscopy studies of the thulium acid pyrophosphate HTmP2O7·3H2O

Crystals of HTmP2O7·3H2O were prepared via a soft chemistry route. Its crystal structure was solved from single-crystal diffraction data. The compound crystallises in the triclinic space group P-1, with the unit cell parameters: a = 6.3724(4) Å, b = 6.8224(3) Å, c = 9.7299(5) Å, α = 82.039(4) °, β = 79.758(5) °, γ = 88.200(4) ° and Z = 2. In its lamellar structure, edge-sharing polyhedra of eightfold coordinated Tm(III) form chains along [010]. These chains are joined in turn to each other using pyrophosphates O-P-O bridges. A network of Osingle bondH…O hydrogen bonds reinforces the cohesion of the structure. The IR spectrum of HTmP2O7·3H2O is interpreted on the basis of characteristic vibrations of PO3 group, POP bridge, and in addition, H2O. The optical properties of HTmP2O7·3H2O were analysed with UV–Vis. The spectrum is characterized by bands corresponding to the transitions starting from the 3H6 ground state to the different higher levels 1G4, 3F2, 3F3, 3H5, and 3F4 of Tm3+ ion