Polyoxometalates turned into polyoxocations
- Synthesis of cationic molybdenum-cobalt heterometallic clusters protected against hydrolysis by macrocyclic triazacyclononane complexes,
Sugiarto, T. Tagami, K. Kawamoto and Y. Hayashi, Dalton Trans., 47, 9657-9664, (2018). DOI: 10.1039/C8DT01226A
Nuclearity control in a decavanadate ligand
- A Highly-flexible Cyclic-decavanadate Ligand for Interconversion of Dinuclear- and Trinuclear-cobalt(II) and Manganese(II) Cores,
T. Maruyama, Y. Kikukawa, H. Sakiyama, M. Katayama, Y. Inada, Y. Hayashi, RSC. Adv., 7, 37666-37674, (2017). DOI: 10.1039/c7ra05941h
A Pd-supported polyoxovanadate
- Synthesis and Characterization of a Palladium-Supported Fluoride-Incorporated Dodecavanadate,
K. Miftahul, Y. Kikukawa, Y. Hayashi, Chem. Lett., 46, 1406-1408, (2017). DOI:10.1246/cl.170594
- Small Molecular Anion Recognition by a Shape-responsive Bowl-type Dodecavanadate,
S. Kuwajima, Y. Kikukawa, Y. Hayashi, Chem. Asian J., 12, 1909-1914, (2017). DOI: 10.1002/asia.201700489
Dodecavanadate bowls revisited
- A Bowl-Type Dodecavanadate as a Halide Receptor,
S. Kuwajima, Y. Ikinobu, D. Watanabe, Y. Kikukawa, Y. Hayashi, and A. Yagasaki, ACS Omega, 2, 268-275, (2017). DOI: 10.1021/acsomega.6b00408
How close can you force two anions together ?
- Synthesis and Structural Characterization of Trimanganese-Containing Polyoxovanadates with Carboxylate Ligands,
T. Maruyama, Y. Kikukawa, K. Kawamoto, and Y. Hayashi, Eur. J. Inorg. Chem., 3, 596-599, (2017). DOI:10.1002/ejic.201601274
Electroabsorption (Stark) Spectra of Transition Metal Complexes,K. Kawamoto, H. Hashimoto, Bull. Jpn. Soc. Coord. Chem., 67, 75-79, (2016). DOI: 10.4019/bjscc.67.75
Play a catch by a molecular mitt
- A chloride capturing system via proton-induced structure transformation between opened- and closed-forms of dodecavanadates,
Y. Inoue, Y. Kikukawa, S. Kuwajima and Y. Hayashi, Dalton Trans., 45, 7563-7569, (2016). DOI:10.1039/C6DT00963H
Deca-, dodeca-, and tridecavanadates
- Structure Transformation among Deca-, Dodeca- and Tridecavanadates and Their Properties for Thioanisole Oxidation,
Y. Kikukawa, K. Ogihara, Y. Hayashi, Inorganics, 3, 295-308, (2015). DOI:10.3390/inorganics3020295
Polyoxovanadate review 2
- Coordination Chemistry of Polyoxovanadates as Inorganic Ligands,
Y. Hayashi, Bull. Jpn. Soc. Coord. Chem., 66, 12-25, (2015). DOI:10.4019/bjscc.66.12
- Synthesis and Characterization of Fluoride-incorporated Polyoxovanadates,
Y. Kikukawa, T. Yokoyama, S. Kashio, Y. Hayashi, J. Inorg. Biochem., 147, 221-226 , (2015). DOI:10.1016/j.jinorgbio.2015.02.010
Disk, Bowl, to Ball
- Structural Conversion from Bowl- to Ball-type Polyoxovanadates: Synthesis of a Spherical Tetradecavanadate through a Chloride-incorporated Bowl-type Dodecavanadate,
T. Kobayashi, S. Kuwajima, T. Kurata, Y. Hayashi, Inorg. Chim. Acta., 420, 69-74, (2014). DOI:10.1016/j.ica.2014.03.035
- Discrete Spherical Hexadecavanadates Incorporating a Bromide with Oxidative Bromination Activity,
N. Kato and Y. Hayashi, Dalton Trans., 42, 11804-11811 (2013). DOI:10.1039/C3DT50521A
Polyoxometalate-based Frameworks with a Linker of Paddlewheel Diruthenium(II, III) Complexes,A. Hashikawa, Y. Sawada, Y. Yamamoto, M. Nishio, W. Kosaka, Y. Hayashi, H. Miyasaka, Cryst. Eng. Comm., 15, 4852-4859 (2013).
Big cations in polyoxovanadate rings
- Early-Lanthanide Complexes with All-Inorganic Macrocyclic Polyoxovanadate Ligands,
M. Nishio, S. Inami, Y. Hayashi, Eur. J. Inorg. Chem., 10, 1876–1881 (2013). DOI:10.1002/ejic.201201435
Coulombic Aggregations of MnIII salen-Type Complexes and Keggin-Type Polyoxometaltes: Isolation of Mn2 Single-Molecule Magnets,Y. Sawada, W. Kosaka, Y. Hayashi, H. Miyasaka, Inorg. Chem., 51, 4824–4832 (2012). DOI: 10.1021/ic300215q
Inorganic Frameworks Made by Combining Paddle-wheel Diruthenium(II, III) Complexes and Polyoxometalate Clusters,Y. Sawada, Y. Yamamoto, M. Nishio, W. Kosaka, Y. Hayashi, H. Miyasaka, Chem. Lett., 41, 212–214 (2012).
Lanthanide complexes with polyoxovanadate ligands
- Lanthanide Complexes of Macrocyclic Polyoxovanadates: Synthesis, Characterization, and Structure Elucidation by X-ray Crystallography and EXAFS Spectroscopy, M. Nishio, S. Inami, M. Katayama, K. Ozutsumi, Y. Hayashi, Inorg. Chem., 51, 784–793 (2012). DOI:10.1021/ic200638f
Reduced hexa-lacunary Dawson complexes
- Isolation of a Stable Lacunary Dawson-type Polyoxomolybdate Cluster,
A. Hashikawa, M. Fujimoto, Y. Hayashi, H. Miyasaka, Chem. Commun., 47, 12361–12363 (2011). DOI:10.1039/C1CC15439G
- Hetero and Lacunary Polyoxovanadate Chemistry: Synthesis, Reactivity and Structural Aspects, Y. Hayashi, Coord. Chem. Rev., 255, 2270–2280 (2011). DOI:10.1016/j.ccr.2011.02.013
Synthesis and Characterization of Chloride-incorporated Dodecavanadate from Dicopper Complex of Macrocyclic Octadecavanadate,T. Kurata, Y. Hayashi, K. Isobe, Chem. Lett., 708–709 (2010). DOI:10.1246/cl.2010.708
Dinuclear Manganese and Cobalt Complexes with Cyclic Polyoxovanadate Ligands: Synthesis and Characterization of [Mn2V10O30]6– and [Co2(H2O)2V10O30]6–,S. Inami, M. Nishio, Y. Hayashi, K. Isobe, H. Kameda, T. Shimoda, Eur. J. Inorg. Chem., 34, 5253–5258 (2009). DOI: 10.1002/ejic.200900609
Formation of V(V) Spherical Polyoxovanadates and Interconversion Reactions of Dodecavanadate Species,K. Okaya, T. Kobayashi, Y. Koyama, Y. Hayashi, K. Isobe, Eur. J. Inorg. Chem., 34, 5156–5163 (2009). DOI: 10.1002/ejic.200900605
Tetrahedral Cobalt(II) and Zinc(II) Chloride with Tetravanadate through a Tripod Coordination Mode,T. Kurata, Y. Hayashi, K. Isobe, Chem. Lett., 218–219 (2009). DOI:10.1246/cl.2009.218
Synthesis of a Bowl-type Dodecavanadate by the Coupling Reaction of Alkoxohexavanadate and Discovery of a Chiral Octadecavanadate,K. Domae, D. Uchimura, Y. Koyama, S. Inami, Y. Hayashi, K. Isobe, H. Kameda, T. Shimoda, Pure. Appl. Chem., 81, 1323–1330 (2009). DOI:10.1351/PAC-CON-08-08-25
Molybdates form various polyoxometalates which represent a molecular entity of metal oxides. In such anions, no structure contained a metal atom with three terminal oxygen atoms is allowed as a consequence of the strong trans influences from M=O multiple bonds, thus it is a structural limitation in polyoxometalates known as Lipscomb's law. We eliminate the restriction by introducing a functional group to provide a chemical protection on the terminal oxygen atoms. By arranging a exceeding number of a cation complex on the surface of a polyoxometalate, polyoxoanions may turn into polyoxocations; a new type of a polyoxometalate framework not available in solution chemistry comes to be possible. It also provides hydrogen bonding network to keep the structure in aqueous solution, just like a structure supporting mechanism in enzyme chemistry.
A flexible inorganic polyoxovanadate ligand makes the coordination mode automatically fit to a multinuclear core. Unlike organic ligands where a tailor-made design such as a binuclear ligand for a binuclear complex is necessary, our inorganic ligand allows coordination mode switches by offering an appropriate number of donors and coordination geometry for a dinuclear or a trinuclear cluster unit, without re-designing the ligand by ellaborating synthetic procedures.
Fluoro-polyoxovanadate frameworks now get two Pd complexes installed on both ends. The all-V(V) framework makes vanadium NMR indespensable tool. It has available coordination sites on Pd(II) and more importantly it is soluble in acetonitrile as a descrete molecule and diamagnetic, with a potential application in MOF and supramolecuar chemistry as a cross-linker unit.
Catch a guest anion of the size even larger than the entrance of the bowl, by squeezing it ! It is flexible and is able to capture various multi-atomic anions. The capturing rates are greater than the capturing of spherical halide ions. The ionic host allows a switch of bond lengths and angles while keeping the overall geometry, it is shape responsive.
The bowl-type vanadium-oxide molecule has a net charge of 4–, yet the inner cavity is positive by the arrangement of 12 vanadium atoms. When a halide anion is added, a host-guest complex is formed by overcoming the overall repulsive interaction. The anion guest sits at the center of the cavity and do not dissociate once it is trapped, "An anion inside an anion".
Two anions naturally repel each other. We have challenged to forcefully connect two 4– anions by a short alkyl chain. Instead of an expecting straight alkyl chain by the result of a repulsive interaction, the alkyl chain was bented to bring two anions actually closer by sandwiching a cation, because the packing pattern minimizes the anionic repulsion. The V-shaped double-anion binds the alkyl ammonium cation through noncovalent interaction.
The vanadium-oxide bowl catches a halide ball then changing a shape to secure it, no longer reactive to the outside reagents. Play a catch, do not fumble a ball. The inorganic bonds are flexible enough to dynamically change bond angles and lengthes in a totally different isomeric structure–––from an open-bowl to a closed-shape just like a move of a mitt in baseball. The process is reversible and you can play it again.
It all appears to be similar in formula. We establish the interconversion reactions among these complexes. The beauty of the ionic complexes in the synthesis is the flexibility of a molecular structure as well as a formulation.
The review on isopolyoxovanadate species including reduced species is presented in Japanese language.
In aqueous polyoxovanadate chemistry, only polyoxovanadates that are stable in an acidic condition is the decavanadate species. No other species is stable in acidic aqueous solution. We discover that the presence of fluoride ion stimulates the equilibrium in a mixed-aqueous solution and produces new fluoro-polyoxovanadate species.
"Umpolung" in chemistry changes a reactivity. The polarity change from a cation binding complex to an anion binding complex was achieved by using a disk-type inorganic complex through the elimination reaction of metal cations by cyanide gas under the presence of an anion. It ultimately constructs a ball-type molecule with a guest anion enclosed inside.
Catalytic oxidation reaction rates increase in a strong acidic condition and the catalyst has to survive. We investigated a polyoxovanadate species produced in such a very strong acidic condition. The isolated descrete hexadecavanadates have a reduced core yet stable under air in nonaqueous solution.
The macrocyclic polyoxovanadate rings incorporate transition matal cations at the center of the ring. When the ionic radius of the metal cations increases up to Lanthanum(III), what happen was the expansion of the vanadium ring size and it was able to adopt a series of big catioins, La(III), Ce(III) and Pr(III). Nine and ten membered-vanadium rings capture those big cations, and the rings show fluxional behaviour.
The descrete lanthanide complexes of all-inorganic system have a polyoxovanadate ring ligand. The VO4 unit in the ring allows to adjust two coordination parameters: i) the coordination bite angles by adjusting ring conformation, ii) the coordination number thorough whether each unit coordinates or not. By alternating the coordination modes, it adopts to fit to the wide ionic-radious range of lanthanide cation series. The ionic complexes keep the descrete structure even in the solution which were confirmed through EXAFS study.
Dawson-type framework may construct from a rubust hexamolybdate. Hexamolybdates are the most fundamental polyoxometalate with six molybdenum(VI) cations arrnaged in Oh symmetry. It should be a good precursor for a new type of polyoxomolybdates, but was too stable in organic solvent. The reduction of the hexamolybdate with acetic acid makes the robust unit rearranged and resulting an isolation of a new lacunary-type Dawson complexes. It has molybdates at the hetero-atom center, with capping acetate ligands at the lacunary sites, a reduced hexa-lacunary-Dawson-type complex.
The review on iso- and heteropolyoxovanadates including lacunary polyoxovanadates.