Hydrothermal synthesis and structures of two layered dioxovanadium(V) phosphates A(VO2)PO4 (A = Ba, Sr)

Dimorphism of the Vanadium(V) Monophosphate PbVO2PO4: α-Layered and β-Tunnel Structures

“…The cell parameters initially measured on Weissenberg "lms and later re"ned by di!ractometric techniques at 293 K with a least-square re"nement based on 25 re#ections are listed in Table 1. The systematic re#ection conditions observed for -PbVO PO , l"2n for h0l and k"2n for 0k0, are consistent with the P2 /c space group, con"rming that it was isostructural with AVO PO (A"Ba, Sr) (10). For -PbVO PO the re#ection conditions k#l"2n for 0kl and h"2n for hk0 are consistent with the space groups Pnma and Pn2 a.…”

“…(VP)O (9), and more recently the compounds SrVO PO and BaVO PO (10). Moreover, the latter could only be prepared by hydrothermal synthesis.…”

“…This behavior is unexpected if one takes into consideration the great ability of V(V) to accomodate various frameworks and suggests that vanadium (V) phosphates should be carefully explored for a better understanding, varying the synthesis methods. Starting from the results obtained by Kang et al (10) for PbVO PO , which was found to be isostructural to the Sr and Ba phases, we have revisited the synthesis and crystal growth of this compound using various methods. We report herein on the dimorphism of this V(V) monophosphate, showing a layered structure built up of VO octahedra and PO tetrahedra for the form prepared by hydrothermal synthesis in agreement with previous results (10), and an original tunnel structure involving VO octahedra and VO and PO tetrahedra for the -form prepared by solid state reaction in air.…”

A Novel Phosphovanadate of Co(III) Hexammine: Co(NH3)6(V1.5P0.5)O6OH

“…At 1092 and 1047 cm\ we "nd the bands due to the asymmetric stretch (PO ) of the phosphate groups, followed by the corresponding symmetric mode (PO ) at lower wavenumbers (19}22). As already shown (23,24), the band wavenumbers corresponding to the (PO ) mode of the phosphate tetrahedra are low due to long P}O bonds generated by interactions between the oxygen atoms and the [Co(NH ) ]> cations. The (PO ) bending can be found at 537 cm\.…”

A Mixed-Valent Vanadium Monophosphate with a Chain-Like Structure: Ba3V2O3(PO4)3

“…In particular, all the phosphates of this system prepared to date by direct synthesis exhibit a tridimensional structure in anhydra phases. This is the case of -and -BaV P O (2-3), Ba V (PO ) (4) and BaVO PO (6). Thus, it seems that the unidimensional structure of Ba VO(PO ) ) H O is stabilized by the presence of H O, which is incorporated during hydrothermal synthesis.…”