Chemical preparation, crystal structure, thermal behavior and IR studies of barium thallium cyclotriphosphate dihydrate

Abstract

Chemical preparation, crystal structure, thermal behavior and IR studies are given for a new barium thallium cyclotriphosphate dihydrate, BaTlP 3O 9·2H 2O. This compound is monoclinic P2 1/ n with the following unit-cell dimensions: a=7.546(3) Å, b=12.105(4) Å, c=11.649(4) Å, β=100.34(3)° and Z=4. Its crystal structure has been determined by X-ray diffraction and refined down to R=0.040, using 1652 independent reflections. BaTlP 3O 9·2H 2O is isotypic to BaNH 4P 3O 9·2H 2O. The thermal behavior of this new salt was studied, between 25 and 600 °C, by infrared spectroscopy, X-ray diffraction and thermal analyses TGA and DTA. BaTlP 3O 9·2H 2O leads, between 300 and 500 °C, to the corresponding anhydrous phase, BaTlP 3O 9. This new phase which is isotypic to BaNaP 3O 9 was characterized by X-ray powder diffraction. It is stable up to its melting point at 560 °C. The IR spectrum of BaTlP 3O 9·2H 2O was examined and interpreted in the domain of the valence frequencies of the cycles, in the light of its proposed crystalline structure, on the basis of our results of the 30 calculated fundamental IR frequencies and of the successive isotopic substitutions of the equivalent atoms (3P, 3Oi, 6Oe of the ring P 3Oi 3Oe 6) for the ring P 3O 9 3− with high symmetry D 3 h .