Exploring the Magnetic Interaction of Asymmetric Structures Based on Chiral V^III₈ Clusters

Abstract

Polyoxovanadates (III) are important class of polyoxometalates in molecular magnetism field, and particularly the systems which contain vanadium­(III) centers. To date, only very few highly reduced vanadium polynuclear complexes were reported, which remains a significant challenge to synthesize novel polyoxovanadates, owing to the characteristics of easily oxidized vanadium­(III). Herein, two unprecedented petaloid chiral octanuclear polyoxovanadates, l- and d-[H2N­(CH3)2]12.5(H3N­(CH2)2NH3)­(H3O)1.5(VIIIμ2-OH)8(SO4)16·2H2O (L-, D-V8 ), have been successfully obtained by solvothermal method without any chiral auxiliary. Both L- and D-V8 compounds contain the motif eight-membered ring (Vμ2-O)8(SO4)16 constituted of three different chiral entangled loops with the V atoms as nodes. Bond valence calculation (BVC) analysis indicates that all the V ions existed in L, D-V8 are +3 value. The magnetic behavior of compounds indicated ferromagnetic coupling between vanadium­(III) ions. To our knowledge, it is the first chiral highly reduced polyoxovanadates that exhibit excellent ferromagnetism.

Lewis Acid Dominant Windmill-Shaped V8 Clusters: A Bifunctional Heterogeneous Catalyst for CO2 Cycloaddition and Oxidation of Sulfides

“…It is the most remarkable feature in that the loss of methoxy groups changes the valence state of the four central V atoms from +4 to +5 calculated by BVC (Table S7). The octahedral V–O and V–N bond distances of the four compounds are in the ranges 1.581–2.461 Å and 2.120–2.166 Å, respectively, which is in accordance with those reported in the previous papers …”

“…Polyoxovanadates (POVs), as one of the most important subclasses of polyoxometaletes (POMs), have attracted more and more attention due to not only the intriguing physicochemical properties, but also the fascinating geometrical features . As Lewis acid (LA) active sites, POVs have catalytic performance. ,, At present, the multifarious nuclears of POVs have been reported in abundance, , while eight-core-based POVs are rarely reported, and the investigations of properties for them are correspondingly limited . Thus, it is meaningful to design and synthesize new-fashioned eight-core-based POVs as bifunctional heterogeneous catalysts for CO 2 cycloaddition and oxidation of sulfides.…”

Sulfate-Bridged, Octanuclear Chromic and Ferric Wheels

“…[(CH 3 ) 2 NH 2 ] 17.4 [SO 4 ] 0.7 [Cr III 8 (μ 2 -OH) 8 (μ 2 -SO 4 ) 16 ] and [(CH 3 ) 2 NH 2 ] 17.4 [SO 4 ] 0.7 [Fe III 8 (μ 2 -OH) 8 (μ 2 -SO 4 ) 16 ] are isostructural and contain the purely inorganic, octameric, ring-like, polyanionic cluster [M III (μ 2 -OH)­(μ 2 -SO 4 ) 2 ] 8 16– , where M = Cr, Fe. These are analogous to the previously reported Ti­(IV) and V­(III) octanuclear molecular wheels. − As a representative, the structure of the eight-membered ferric wheel [Fe III 8 (OH) 8 (SO 4 ) 16 ] 16– is shown in Figure . The tilted octametallic wheels are stacked along the crystallographic a axis.…”

“…While the vast majority of molecular wheels are bridged by organic ligands, those connected by sulfate ions are quite rare . So far, the {Ti 8 } and {V 8 } wheels are the only known examples of discrete inorganic rings with bridging sulfate ions. − Recently, we reported the anionic octanuclear wheel [V 8 (OH) 8 (SO 4 ) 16 ] 16– which has the largest ground-state magnetic spin known to date ( S t = 8) among homonuclear vanadium-based complexes . Extending our research to other 3d metals, we describe here the syntheses, crystal structures and magnetic properties of new octameric “chromic” and “ferric wheels” in which metal centers are linked by sulfato and hydroxo ligands.…”

Synthesis, Crystal Structure, and Electrochemical Properties of an Isopolyoxovanadate Compound Modified Transition-Metal Complex Based on [V4O12]4−

“…Among POMs, isopolyoxovanadates are regarded as very important because of their outstanding magnetic and electronic properties and the profound impact of their long-term promise as oxidation catalysts [6]. In comparison with other POMs, the vanadium oxygen clusters exhibit unique structure and excellent performance due to the variable valence (from +3 to +5) and abundant coordination configurations (VO 4 tetrahedra, VO 5 square pyramid and trigonal bipyramid, VO 6 octahedra) of vanadium atom [7][8][9][10][11][12]. Var- 12− and so on, have been reported in the previous papers [13][14][15][16][17][18][19][20][21][22][23][24][25].…”