Syntheses, Structures And Performances Of Non-classical Tungsten(Molybdenum)-Vanadium-Oxygen Clusters

Polyoxometalates (POMs) represent a fascinating class of inorganic chemistry with a structural variety and interesting properties, which are of use in fields as diverse as catalysis, sorption, molecular electronics, medicine, etc. As the applications of hydrothermal technique on the syntheses, various organic-inorganic hybrid materials of particular properties emerges constantly and much attention has been caused on the performances studies of various materials. In this field, an important advance is to decorate well-known polyoxoanions with various organic and/or transition metal complex moieties and then to link them up into one-, two-, even three-dimensional extended solid materials in appropriate ways. The introduction of metal complex can not only enrich the frameworks of polyoxometalates but also ameliorate their electronic and mangnetic properties. Based on this mechanism, we synthesized some non-classical metal-oxygen clusters, the cluster-polymers based on tungsten-vanadium and molybdenum-vanadium oxygen clusters. On the bases of X-ray structural analyses, some central compounds have been characterized by IR, XPS, EPR, XRD spectra. The thermal analyses and magnetic properties of some compounds have been studied, which would take an important role in the explorations of structures and functions for the compounds.I non-classical tungsten-vanadium oxygen clustersApplying in hydrothermal synthesis reactions, we synthesized six non-classical tungsten-vanadium oxygen clusters. [Cu(en)2]2[CuWVI5WV4VIV7O44{Cu(en)2 (H2O)}2]·4H2O 1, [Cu(en)2(H2O)] [Cu0.5(en)]3[CuWVI9WVVIV4O42{Cu(en)2}]·3H2O 2, (H2en)2(H3O)7[WVI6VVVIV8O42]·2H2O 3, [Zn(en)2(H2O)]3[WVI5WV5VVVIV4O42 {Zn(en)2}] 4, [Fe(phen)3]2[WVI8.5WV2VVVVI3.5O42]·3H2O 5, [Fe(phen)3]2 [WVI10VVI5O42]·6H2O 6. Compound 1 is composed of the [CuWVI5WV4VIV7O44 {Cu(en)2(H2O)}2]4-, which is further linked into a novel 2D layer through four [Cu(en)2]2+ fragments. The sturucture of compound 2 features a novel 2D layer built from the bicapped Keggin [CuWVI9WVVIV4O42]7- anions are decorated with [Cu(en)2]2+ unit, which is further interconnected by three [Cu(en)2]2+ groups via the terminal oxygen atoms and double- bridge atoms of clusters. In the crystal structure of 3, the reduced bicapped Keggin [WVI6VVVIV8O42]11- units having a high V/W ratio are connected by (μ2-O)2 oxygen atoms forming 1D chains. Compound 4 represents the first example that an unusual reducted bicapped Keggin [WVI5WV5VVVIV4O42]8- cluster is covalently bonded to a [Zn(en)2]2+ unit via the surface bibridged oxygen atoms. The polyoxoanions of Compounds 5 and 6 are decorated with [Fe(phen)3]2+ cations, and both of them have analogous structure to each other with slightly different packing modes of polyoxoanions, [Fe(phen)3]2+ cations and water molecules. They are further linked to from 2D supramolecular networks through hydrogen bonging. The X-ray single crystal analysis, elemental analysis, IR, XPS, EPR, XRD and TG etc., have been performed on these compounds. Variable-temperature magnetic susceptibility measurements of compound 1, 2 and 3 reveal the feature of antiferromagnetic exchange.II non-classical molybdenum-vanadium oxygen clustersApplying in hydrothermal synthesis reactions, we synthesized ten non-classical tungsten-vanadium oxygen clusters. H3{[MoVI8VIV6O36(PO4)][Cu(en)2]4}(MoO4)·4H2O 7, [Cu(en)2]{[Cu(en)2]2[MoVI5MoV3VIV8O40(PO4)]}·4H2O 8, [Co(en)2] {[Co(en)2]2[HMoVI4MoV4VIV8O40(PO4)]}·5H2O 9, [Co(en)3]2[H3PMoVI8VIV6O42]·H2O 10, [Ni(en)2]{[Ni(en)2]2[MoVI5MoV3VIV8O40(VO4)]}·2H2O 11, [Ni(en)2] {[Ni(en)2]2[MoVI5MoV3VIV8O40(VO4)] }(dien)·H2O 12, [{[Cu(en)2][Cu(en)2(H2O)] [SiMoVI8VIV6O42]}2{[Cu(en)2]0.5}][Cu(en)2][Cu(en)2(H2O)]·H2O 13, (H2en)2 (H3O)12[SiMoVI14MoV2VV2VIV10O84] 14, [Ni(en)2]{[Ni(en)2]2[MoVI6MoV2VIV8O40 (SiO4)]}(dien)·2H2O 15, [Co(en)3]2[SiMoVI8VV4VIV2O42]·6H2O 16. These compounds can be grouped into three systems. The compounds 7-10 belonging to the P/Mo/V/ O system have been synthesized. Compound 7, which has 3D network structure, is based on the molybdenum-vanadium cluster of bicapped Keggin structure linked by the transition metal complex ion [Cu(en)2]2+ bridges. The isomorphic compounds 8 and 9 feature a 1D chain built from the reduced tetra-capped pseudo-keggin polyoxoanion, which is further interconnected by [M(en)2]2+ (M = Cu, Co) groups via the terminal oxygen atoms of polyoxoanions. Compound 8 and 9 represent the first 1D chain constructed from the reduced P/Mo/V/O tetra-capped Keggin polyoxoanions and [M(en)2]2+ (M = Cu, Co) cations. Compound 10 is a discrete cluster compound with bicapped Keggin structure P/Mo/V/O cluster, and [Co(en)2]2+ complex ion act as the balanced cations. The compounds 11-12 belonging to the Mo/V/O system have been synthesized. Compound 11 belongs to the polymer of cluster with 1D chain structure based on tetra-capped Keggin cluster units linked through the bridged [Ni(en)2]2+ groups. The compound 12 is isomorphic with 11, and the differences between compound 11 and 12 are having dien in 12 and the amount of lattic water molecules. The compounds 13-16 belonging to the Si/Mo/V/O system have been synthesized. Compound 13 exhibits a unique 1D organic-inorganic hybrid chain containing double-supporting bi-capped Keggin polyoxoanion dimer linked by transition metal coordination fragments. Compound 14 is also possessed of 1D structure based on dimerized bi-capped Keggin cluster consisting of two kinds of polyoxoanion units having different valence states, [Si(1)MoVI6MoV2VIV6O42]10- and [Si(2)MoVI8VV2VIV4O42]6-, and linked by two terminal oxygen atoms from two dimerized cluster units. These two compounds represent the first 1D derivatives based on dimerized bi-capped Keggin-type polyoxoanion in the Mo/V/Si/O system under hydrothermal condition. Compound 15 is isomorphic with compound 8, except that Cu, P atoms are replaced by Ni and Si atoms, respectively. Charge distribution of Mo atoms in polyoxoanion of 15 is different from that in 8 and these result in somewhat different corresponding bond distance in 15 and 8. Compound 16 is a discrete cluster compound with bicapped Keggin structure Si/Mo/V/O cluster, and [Co(en)2]2+ complex ion act as the balanced cations. The X-ray single crystal analysis, elemental analysis, IR, XPS, EPR, XRD and TG etc., have been performed on these compounds. The magnetic behavior of compounds 8, 11 and 13 were measured, and these data between 50 K and 250 K is coincident with the Curie-Weiss law, the Weiss Constant is small than zero, which indicates the presence of antiferromagnetic interaction between the metal ions of them. Unfortunately, it is too difficult to fit the experimental mangentic data of these hetero-polymetallic spin systems using a suitable theoretical model.III non-classical vanadium oxygen clustersApplying in hydrothermal synthesis reactions, we synthesized two non-classical vanadium oxygen clusters. [Ni(en)2]3[VV7VIV11O42CI]·8H2O 17 and [Cu(en)2]2 [VV6VIV4O25] 18. Compound 17 exhibits an interesting 3D supramolecular framework assembled by sinusoidal-like arrangement of 2D coordination polymer layers and cryatal water molecules. Compound 18 features a 3D network built from 2D inorganic layer-like structure interconnected via [Cu(en)2]2+ units. The X-ray single crystal analysis, elemental analysis, IR, XPS, EPR and TG etc., have been performed on both compounds. The magnetic behavior of compound 17 was measured, and the data indicates the existence of stronger antiferromagnetic coupling of eleven V(IV) and three Ni(II) ions.