Synthesis, Structure, and Solubility Studies of a New Arsenato‐Polyoxovanadate Cluster Compound: (NH₄)₄[V₁₂As₈O₄₀(H₂O)]·4H₂O

Abstract

Abstract. The new arsenato polyxoxvanadate (NH4)4[V12As8O40(H2O)]·4H2O (1) was obtained under solvothermal conditions using either a mixture of ethyl ether/H2O or ethanol/H2O acting as reducing agents. Compound 1 crystallizes in the orthorhombic space group Pnnm with a = 13.6740(3), b = 12.7378(5), c = 13.0580(3) Å, V = 2274.40(11) Å3, Z = 2. The central structural motif features an anionic cluster shell, which can be derived from the {V18O42} archetype cluster by replacing VO5 polyhedra by As2O5 units and omitting two VO5 square pyramids. The electronic situation of the cluster anion can be best described by the formula [V8IVV4VAs8IIIO40(H2O)]4–. The charge neutrality of the compound is achieved by NH4+ cations which occupy the free space between the clusters together with crystal H2O molecules. Thermal investigation shows a complex decomposition process occurring in at least three steps. Determination of the optical band gap classifies 1 as a semiconductor with a band gap of 2.8 eV. Solubility studies accompanied by IR spectroscopy, ESI‐MS, X‐ray powder diffractometry and elemental analysis demonstrate that the cluster is partially dissolved.

Controlling Nucleation and Crystal Growth of a Distinct Polyoxovanadate Cluster: An In Situ Energy Dispersive X‐ray Diffraction Study under Solvothermal Conditions

“…With increasing amine concentration, more V V species can be reduced leading to the sequence: [V 14 Sb 8 O 42 ] 4− (75 %, 77.5 %), [V 15 Sb 6 O 42 ] 6− (77.5 %), and [V 16 Sb 4 O 42 ] 8− (80 %; Figure 10). Although syntheses performed under static conditions require adjustments of the educt ratios,29, 32, 54 this synthesis parameter seems to be unimportant under dynamic reaction conditions. For a given amine concentration, the reaction temperature plays no role, at least for the temperature range investigated herein.…”

“…The range of potential applications of POVs covers areas form medicine to catalysis. [33] A literature search showed that most POVs are synthesized under solvothermal conditions, [29][30][31][32][34][35][36][37] in contrast to polyoxometalates based on Mo or W.…”

“…During the last few years, more attention was drawn to chemical reactions under in situ conditions to acquire a detailed picture about the reaction and crystallization mechanisms 1–28. Since few years, we are synthesizing polyoxovanadates (POVs) and especially POVs modified by heteroatoms (As29, Ge30, Sb31, 32) under solvothermal conditions. The range of potential applications of POVs covers areas form medicine to catalysis 33.…”

In situ ligand exchange-mediated 0D/1D transformation of a polyoxovanadate

“…Si, Ge, As, or Sb. 1 Charge compensation of the negatively charged POV clusters is realized by ammonium, [2][3][4] alkali metals cations, [5][6][7][8] protonated amine molecules [9][10][11][12] or transition metal amine complexes. [13][14][15] There are also reports that bond formation between the POV cores and cations [16][17][18] leads to charge-neutral complexes.…”

An Exotic Layered Compound Consisting of Interconnected Arsenato‐Polyoxovanadate Clusters: Thermal and Magnetic Properties and Liquid Phase Exfoliation

“…The most common clusters of As‐POVs are {V 12 As 8 O 40 }, [28,31,38–43] {V 14 As 8 O 42 }, [10,12,13,22–35] {V 15 As 6 O 42 } [9–17,44] and {V 16 As 4 O 42 } [3] . We note that the structure of {V 12 As 8 O 40 } is not related to that of {V 18 O 42 } [2] .…”