Synthesis and structural characterization of AMV₂O₈(A = K, Rb, Tl, Cs; M = Nb, Ta) vanadates: a structural comparison of A⁺M⁵⁺V₂O₈vanadates and A⁺M⁵⁺P₂O₈phosphates

Abstract

Eight new quaternary vanadates of niobium and tantalum, AMV2O8 (A = K, Rb, Tl, Cs; M = Nb, Ta), have been prepared by solid state reactions and structurally characterized by single crystal and powder X-ray diffraction (XRD) techniques. The two cesium compounds, unlike the known CsSbV2O8 with a layered yavapaiite structure, have a new three-dimensional structure and the other six compounds possess the known KSbV2O8 structure type. The three types of [(MV2O8)(-)]∞ anionic frameworks of twelve A(+)M(5+)V2O8 (A = K, Rb, Tl, Cs; M = Nb, Ta, Sb) vanadates could be conceived to be built by different connectivity patterns of M2V4O18 ribbons, which contain MO6 octahedra and VO4 tetrahedra. A structural comparison of these twelve vanadates and the nineteen A(+)M(5+)P2O8 phosphates has been made. The spectroscopic studies of these eight new quaternary vanadates are presented.

Syntheses and Characterization of AM2V2O11 (A = Ba, Sr, Pb; M = Nb, Ta) Vanadates with Centrosymmetric and Noncentrosymmetric Structures

“…A synthetic and structural study of known and new quaternary AM 2 V 2 O 11 (A = Ba, Sr, Ca, Pb, Cd; M = Nb, Ta) vanadates is considered worthy and, therefore, undertaken from the point of view of (i) isolation of new isomorphous compounds, (ii) their structure determination for identification of probable new structure types, and (iii) evaluation of the SHG responses of those compounds, if any, with noncentrosymmetric structures. Moreover, such a study is in line with our previous synthetic and structural investigation on AMV 2 O 8 (A = K, Rb, Cs, Tl; M = Nb, Ta) vanadates of niobium and tantalum. The present study pertains to four known compounds, BaNb 2 V 2 O 11 ( 1 ), BaTa 2 V 2 O 11 ( 2 ), SrNb 2 V 2 O 11 ( 3 ), and SrTa 2 V 2 O 11 ( 4 ), and one new PbTa 2 V 2 O 11 ( 5 ) compound.…”

“…The infrared and Raman spectral features of these vanadates 2 – 5 are assigned as per the literature reports on phosphates ,− and vanadates . Raman spectra (Figure S6) contain the stretching and bending modes of vibration, both symmetric and asymmetric, of the VO 4 tetrahedron in the ranges of 953–1020 and 400–560 cm –1 , respectively.…”

Synthesis, Structure, and Antibacterial Activity of a Thallium(III)-Containing Polyoxometalate, [Tl2{B-β-SiW8O30(OH)}2]12–

“…Thallium­(I) salts of conventional POMs such as the Keggin ion, paratungstate, and metatungstate have been prepared . Thallium-containing metal oxides with extended structures or Zintl phases containing thallium have also been reported . In 1953, Magneli first described the structure of hexagonal tungsten bronze A x WO 3 , and later Shivahare (1964) and Bierstedt et al (1965) isolated Tl 2 W 4 O 13 and Tl 0.3 WO 3 , respectively.…”

Synthesis, Crystal Structure, and Characterizations of Two Tantalum Phosphates A3TaP2O9 (A=K, Na)

“…The (O 4 Ta)–O–(TaO 4 ) connection is reinforced by two PO 4 groups to form the (TaP 2 O 9 ) ∞ chains running along the b direction, with K + ions filling between the chains (a–c). In the structure, Ta and six O atoms coordinate to form a TaO 6 octahedron with the bond lengths varying from 1.942(3) to 1.980(6) Å, which is observed in the tantalum-based oxides such as Li 6 KTaO 6 , KTaGe 3 O 9 , Li 5 La 3 Ta 2 O 12 , Sr 3 MgTa 2 O 9 , and CsTaV 2 O 8 . − P is attached to four O atoms to form a PO 4 tetrahedron with bond lengths from 1.467(11) to 1.603(7) Å. In K 3 TaP 2 O 9 , there are five kinds of K + ions, the K + (2), K + (3), K + (4), and K + (5) cations are surrounded by six oxygen atoms, and K + (1) is surrounded by seven, with bond lengths from 2.513(11) to 3.352(9) Å, maintaining valence balance within the network.…”