Synthesis And Properties Of Polyoxometalate-based Cyanide-bridged Transition Metals Complexes

Polyoxometalates(POMs) represent a fascinating class of inorganic materials with enormous range of size and structure and excellent physical and chemical properties, such as redox properties, nucleophilic oxygen-enriched surfaces, high negative charge and adjustable p H. Lacunary polyoxometalates are good candidates for the encapsulation of electrophilic dand f-block metals and other inorganic fragments, leading to the products with interesting catalysis and magnetic properties. Cyanide, as a short and conjugate ligand, is an excellent bridging ligand for effectively transmitting magnetic coupling. Therefore, in this dissertation we using lacunary polyoxometalates as penta-dentate ligand to encapsulate the metal-cyano fragments, to prepare several novel compounds.Twelve new compounds have been synthesized via conventional aqueous solution methods. The compounds were characterized by UV-vis, single crystal X-ray diffractions, elemental analyses, IR, and TG.1. Two cyanide-bridged heteropolymolybdate complexes have been synthesized by a facile self-assembly process in aqueous solution:H2Na2(C4H10ON)22[{FeIII(CN)6}·(FeIII0.25MnII0.75 Ge Mo11O39)4]·16H2O(1)Na2(C4H10ON)21[{FeIII(CN)6}·(FeIIIGe Mo11O39)4]·CH3CN·11H2O(2)The two compounds 1-2 are isomorphous. The polyoxoanion can be formulated as four {MGe Mo11O39}(M = FeIII, MnII) subunits and one [FeIII(CN)6]3- unit, exhibiting a “flower-like” structure. Magnetic investigation showed that complex 2 exhibits slow magnetic relaxation behavior. The surface photovoltage spectra(SPS) demonstrate that compounds 1–2 should be of p-type semiconductors, suggesting they may be to become photocatalysis and light-to-electricity conversion materials.2. Four new complexes have been synthesized via“one-pot reaction” method and“building block” method.H3(C4H10ON)20[{Fe(CN)6}(PW11O39Mn)4]·(CH3CN)2·18H2O(3)H4(C4H10ON)19[{Fe(CN)6}(PW11O39Ni)4]·CH3CN·15H2O(4)K(C4H10ON)15[HN(CH2CH2OH)3]11[{Fe(CN)6}(Si W11O39Mn)4]·12H2O(5)K(C4H10ON)14[HN(CH2CH2OH)3]12[{Fe(CN)6}(Si W11O39Ni)4]·9H2O(6)The two compounds 3-4 are isomorphous. The polyoxoanion can be view as a central [MII4FeIII(CN)6]5+(M = Mn, Ni) moiety stabilized by four monolacunary [α-PW11O39]7- units. The two compounds 5-6 can also be considered as one paramagnetic cluster [MII4FeIII(CN)6]5+(M = Mn, Ni) with four magnetic insulative [α-Ge Mo11O39]8- ligands. Compound 5 exhibits a one-dimensional chain-like framework. Compound 6 exhibits a two-dimensional framework.3. Three new complexes based on Dawson-type polyoxometalate have been synthesized via “building block” method.(C4H10ON)23[HN(CH2CH2OH)3]11H[FeIII(CN)6(α2-P2W17O61NiII)4]·31H2O(7)(C4H10ON)23[HN(CH2CH2OH)3]10H2[FeIII(CN)6(α2-P2W17O61CoII)4]·27H2O(8)K(C4H10ON)20[HN(CH3)3]14[FeIII(CN)6(α2-P2W17O61MnII)4]·15H2O(9)The two compounds 7-8 are isomorphous. The polyoxoanion can be view as a central [MII4FeIII(CN)6]5+(M = Ni, Co) moiety stabilized by four monolacunary [α2-P2W17O61]10-units. In compound 9, two polyoxoanions was further connected by K+ into a cube shape cage. Magnetic study reveals that the antiferromagnetic interaction exists in compound 7, ferromagnetic exchange interaction in compounds 8 and ferrimagnetic exchange interaction in compounds 9.4. To explore the coordinately assemble cyanometalate anions with the polyoxometalate B-[Sb W9O33]9-, we obtained three new compounds based on {Sb W9}.K2Na10(C4H10ON)9(C2H8N)6[Fe11(H2O)14(OH)2{(Sb W9O33)3(W3O10)}2]·24H2O(10)K2Na17(C4H10ON)8[Fe11(H2O)14(OH)2{(Sb W9O33)3(W3O10)}2]2·36H2O(11)Na5.2(C4H10ON)2[Mn2.8W1.2(OH)2(H2O)8(B-β-Sb W9O33)2]·20H2O(12)Complexs 10 and 11 all contain a trimeric fans-type [K(Sb W9O33)3(W3O10)Fe5(H2O)6]13-. Furthermore, two trimmers aggregated into hexamers by O-Fe-O bridges and the hexamers aggregated into 2-D layer. Complexs 10 and 11 represent the first example a hexameric fans-type compounds based on {Sb W9}. Complexs 12 present offset sandwich structure based on {Sb W9} building unit.