Synthesis And Characterization Of Transition Metal Substituted Lacunary Tungsten-oxo Clusters

The research work of this dissertation is directed by the idea of lacunary directed synthesis that the lacunary sites of various polyoxometalate?POM?precursors may act as the structure directing agents and induce different metal ions to form novel clusters which was first summarized by our group under the practice and experience of the exploration on the metal-oxo cluster recent years.We introduced different kinds of tungsten-oxo lacunary precursors and the second type of metal ions into the hydrothermal reaction system,expecting to obtain novel high-nuclear metal substituted tungstate-oxo clusters,aggregates.Under the guidance of the above mentioned idea and the hard work,we successfully obtained three series of novel metal substituted tungsten-oxo clusters,which were characterized by spectroscopies,structures,thermal and relevant properties.The successful syntheses of these compounds not only enrich the structural type and synthetic idea of tungsten-oxo cluster chemistry,but also provide a novel route for the development of tungsten-oxo cluster chemistry.Series 1:Six discrete organic ligands functioned hexa-nickel-substituted POMs[Ni₆??₃-OH?₃?EG?₂?enMe?₂?Dpta?(B-?-PW₉O₃₄)]·2H₂O?3-1?H₄[Ni?enMe??H₂O?₄][Ni₆??₃-OH?₃?H₂O?₂?enMe?₂?py?₅(B-?-SiW₉O₃₄)]·H₂O?3-2?and H₄[Ni_0.5?enMe?][Ni₆??₃-OH?₃?H₂O??enMe?₃?py?₄(B-?-SiW₉O₃₄)]·7H₂O?3-3?have been isolated under hydrothermal conditions.Optical band gap measurement of 3-1 to 3-2 suggests that they have the semiconductive characteristics.Series 2:Two organic-inorganic hybrid mono-cobalt-substituted POMs[Cu?en?₂?H₂O?]₂{[Cu?en?₂]₄(CuSiW₁₁O₃₉)₂}·6H₂O?3-4?and H₂[Cu?en?₂][Cu?en??H₂O?₃]₂[Cu?en?₂?H₂O?]₄(P₂W₁₇CuO₆₁)₂·2H₂O?3-5?have been isolated under hydrothermal conditions.Compound 3-4 exhibits a 2-D sheet structure including the array of–A–B–A–C–an d–A–B–A–B–,in which the[CuSiW₁₁O₃₉]^6-and[Cu?en?₂]²⁺cations as the linkers.Compound 3-5 have a 1-D chain structure via W/Cu–O–W/Cu bond and transition metal cation.Series 3:Three zirconium-substituted sandwich POMs,?TMA?₄H₆[{SiW₁₁O₃₉Zr??-OH?}₂]·8H₂O?3-6??TMA?₂H₇[Zr₃??-OH?₃(A-?-PW₉O₃₄)₂]·6H₂O?3-7?H₁₂[Zr₄O₂?OH?₂?C₂O₄?₂(?-SiW₁₀O₃₇)₂]·2H₂O?3-8?have been isolated under hydrothermal conditions.They are zirconium-substituted sandwich POMs and achieve the synthesis from Zr₂-substituted sandwich POMs from Zr₄-substituted sandwich POMs.The successful syntheses of these novel compounds further confirms that not only the hydrothermal technique is an effective synthetic method in the POM field,but also the utilization of multi-dentate ligands is an effective strategy to design and make metal-subsitituted POMs,which endows us with a great opportunity and challenge in exploiting and making more novel organic-inorganic hybrid POM derivatives by means of the appropriate choice of different lacunary POM precursors and various organic ligands.