Syntheses, Structures And Properties Of Non-classical Metal-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. The metal oxygen clusters have been employed to constructed novel molecules based function materials owing to their particular Physical chemistry properties. 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 supramolecular, supported and extended solid materials in appropriate ways. Based on this mechanism, we synthesized some non-classical metal-oxygen clusters, the polymer of clusters and supramolecular 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 spectra and thermal analyses. The 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. Molybdenum (tungsten)-oxygen clustersApplying in hydrothermal synthesis reactions, we synthesized three non-classical molybdenum-oxygen clusters and three hetero-tungsten-oxygen clusters.β–Mo8O26 [Cu(en)(1,10-phen)(H2O)]2 1, {(CoO4)Mo12O26(μ2-OH)10)}[Co(H2O)3]4·27H2O 2, (Him)2(H3O)2[PMo12O40Sb2] 3, {(HPW12O40)[Cu4(2,2'-bpy)4(PO4)2(H2O)2]}n·nH2O 4, VW12O40[Cu(en)2(H2O)]3 5, SiW12O40[Cu(en)2(H2O)]3 6. Compound 1 is composed of the bi-supportedβ–Mo8O26 units, which are further linked into a novel 3D supramolecular layer through hydrogen bonding andπ···πstacking interactions. Compound 2 exhibits neutral tetra-cappedε-Keggin-type POM, which is based on rare fully-reducedε-Keggin core {(CoO4)Mo12O26(μ2-OH)10)}8- with four additional coordination complexes [Co(H2O)3]2+. Compound 3 represents the second example of bi-cappedα-Keggin structure POM by antimony atoms. The [PMo12O40Sb2] units link each other by Sb–O weak-bonding to extend into two dimensional inorganic layer structures. To our knowledge, the two-dimensional inorganic layer structure based on antimony-containing POMs is rather scarce. Compound 4 is a novel three-dimensional supramolecular framework based on tetra-copper phosphate cluster throughπ···πstacking interactions, and classical POM [HPW12O40]2– is filled into holes act as templates. Compounds 5 and 6 are isomorphic; they represent the first example classical Keggin polyoxoanion supported by three transition metal complex moieties, which further act as the neutral molecular unit for the construction of the interesting classical distorted cubic (α-Po) net. The X-ray single crystal analyses, elemental analysis, IR, XPS, EPR and TG etc., have been performed on these compounds. Variable-temperature magnetic susceptibility measurements of compound 2, 4 and 5 reveal the feature of antiferromagnetic exchange.II. non-classical tungsten-vanadium oxygen clustersApplying in hydrothermal synthesis reactions, we synthesized six non-classical tungsten-vanadium oxygen clusters. [VW12O40][Ni(phen)3]3·15H2O 7, {PW8V6O42 [Cu(en)2(H2O)]2}[Cu(2,2'–bpy)2]3·6H2O 8, [Ni(phen)3][Ni(en)3][Ni(en)2(H2O)2][Ni (en)2]0.5[PWVI7WV2VIV3O40(VIVO)2]·6H2O 9, [Ni(phen)3]2[Ni(en)2]Na[PWVI7WV2 VIV3O40(VIVO)2]·8H2O 10, [HPW7V9O44][Fe(2,2'–bpy)3]2(im)4·5H2O 11, [HPW5V13 O46][Fe(2,2'–bpy)3]2(im)2·6H2O 12. The basic unit of compound 7 possessing classical Keggin structure contains a distorted central VIVO4 tetrahedron and 12 coordination distorted WO6 octahedra. The fundamental unit of compound 8 exhibits a bi-capped and bi-supported Keggin structure, which further acts as the building unit for the construction of the interesting 2D supramolecular network through hydrogen bonding andπ···πstacking interactions. Compounds 9 and 10 are based on same W/V/O polyanion unit [PWVI7WV2VIV3O40(VIVO)2]7– possessing bi-capped Keggin structure. Interestingly, compound 9 contains four different kinds of nickel complex counteractions. In compound 9, POMs are employed to construct the 3D hydrogen-bonded host networks, the guest TMCs are incorporated into the host networks through hydrogen-bonding interactions. Compound 10 shows an interesting 3D supramolecular TMCs-sandwich structure. The polyoxoanion unit of compounds 11 and 12 is tetra-capped and hexa-capped Keggin tungsten-vanadium POMs, respectively. In compounds 11 and 12 possessing similar crystal structure, POMs, H2O and im are employed to construct the 3D hydrogen-bonded host networks, the guest TMCs are incorporated into the host frameworks. Compound 12 is the first example of mixed W/V hexa-capped super-Keggin structural POM. The X-ray single crystal analyses, elemental analysis, IR, XPS, EPR and TG etc., have been performed on these compounds. In addition, variable-temperature magnetic susceptibility measurements of compound 8 and 12 have been investigated.III. non-classical molybdenum -vanadium oxygen clusters Applying in hydrothermal synthesis reactions, we synthesized seven nonclassical tungsten-vanadium oxygen clusters. [Co(phen)3][Co(en)3][Co(en)2(H2O)2][Co (en)2]0.5[PMoVI8VIV6O42]·6H2O 13, (im)2{H4(VIVO4)MoVI8VIV4O36(VIVO)2 [Ni(phen)2 (im)]2}H2O 14, {PMoVI7MoV5O40(VIVO)2}[Cu(2,2'-bpy)2]2 15, Na4[(VIVO4)MoV12 O40(VIVO)6] 16H2O 16, {PMoVI8VV3VIVO40(VIVO)2[Co(2,2'-bpy)2(H2O)]2}{PMoVI8 VV3VIVO40(VIVO)2}[Co(2,2'-bpy)3]2·10H2O 17, {PMo8VV3VIVO40(VIVO)2 [Ni(2,2'- bpy)2(H2O)]2}{PMoVI8VV3VIVO40(VIVO)2}[Ni(2,2'-bpy)3]2·10H2O 18, [{PMoVI8 VIV3 VVO40(VIVO)2[Cu(en)(2,2'-bpy)]2}{PMo8VIV3VVO40(VIVO)2}{[Cu(en)(2,2'-bpy)]2}] [Cu(en)2(H2O)2(4,4'-bpy)·2H2O 19. Compound 13 exhibits interesting 3D supramolecular network based on bi-capped Keggin-type Mo/V/O cluster, and the template transition-metal complexes (TMCs) being generated in situ are filled in the channels. The fundamental unit of compound 14 exhibits a bi-capped and bi-supported Keggin structure, which further acts as the neutral molecular unit for the construction of the interesting 3D supramolecular network through hydrogen bonding andπ···πstacking interactions. Compound 15, which has 2D network structure, is based on the Keggin-type molybdenum-vanadium cluster linked by the transition metal complex ion [Cu(2,2'-bpy)2]2+ bridges. Compound 16 is the unique fully reducedα-Keggin POMs, and the [VIVMoV12(VIVO)6]4? anion is the first mixed Mo/V hexa-capped super-Keggin polyoxoanion. In the fundamental unit of isomorphic compounds 17 and 18, there are two types of cluster anions, one is bi-capped Keggin type and another is bi-capped & bi-supported Keggin type. The POM unit of compound 19 is similar to 17, and it is worthwhile noting that two type cluster units linked through [Cu(en)(2,2'-bpy)]2+ fragments to extend into 1D chain. To the best of our knowledge, 19 represent the first example of extended structure constructed from two type polyoxoanions. The X-ray single crystal analyses, elemental analysis, IR, XPS, EPR and TG etc., have been performed on these compounds. In addition, variable-temperature magnetic susceptibility measurements of compound 13, 17, 18 and 19 have been investigated.