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Sartzi H, Long DL, Sproules S, Cronin L, Miras HN. Directed Self-Assembly, Symmetry Breaking, and Electronic Modulation of Metal Oxide Clusters by Pyramidal Heteroanions. Chemistry 2018; 24:4399-4411. [PMID: 29315925 DOI: 10.1002/chem.201705711] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Indexed: 11/06/2022]
Abstract
Mixed valence/metal polyoxometalate (POM) clusters are one of the most interesting host species because they show the ability to incorporate a wide range of heteroatoms of various charges and geometries. We report herein the incorporation of pyramidal EO32- heteroanions (E=PH, S, Se, Te) that are responsible not only for directing the templated assembly of a family of mixed-metal POMs but also for the symmetry-breaking of the traditional Dawson architecture and modulation of the electronic characteristics of the cluster's shell. The isolated family of POMs consists of four members: (Me2 NH2 )5 Na2 [Mo11 V7 O52 (HPO3 )]⋅MeOH⋅5 H2 O (1), (NH4 )7 [Mo11 V7 O52 (SO3 )]⋅12 H2 O (2), K7 [Mo11 V7 O52 (SeO3 )] ⋅31 H2 O (3), and (Me2 NH2 )6 Na[Mo11 V7 O52 (TeO3 )]⋅15 H2 O (4), and were characterized by X-ray structural analysis, electrospray ionization mass spectrometry (ESI-MS), thermogravimetric analysis (TGA), UV/Vis, FTIR, elemental analysis, flame atomic absorption spectroscopy (FAAS), and inductively coupled plasma optical emission spectroscopy (ICP-OES). Cyclic voltammetry (CV) and electron paramagnetic resonance (EPR) spectroscopic studies in concert with density functional theoretical (DFT) calculations have been used to elucidate the effect of the heteroatom on the electronic properties of the cluster.
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Affiliation(s)
- Harikleia Sartzi
- WestCHEM, School of Chemistry, University of Glasgow, University Avenue, Glasgow, G12 8QQ, UK
| | - De-Liang Long
- WestCHEM, School of Chemistry, University of Glasgow, University Avenue, Glasgow, G12 8QQ, UK
| | - Stephen Sproules
- WestCHEM, School of Chemistry, University of Glasgow, University Avenue, Glasgow, G12 8QQ, UK
| | - Leroy Cronin
- WestCHEM, School of Chemistry, University of Glasgow, University Avenue, Glasgow, G12 8QQ, UK
| | - Haralampos N Miras
- WestCHEM, School of Chemistry, University of Glasgow, University Avenue, Glasgow, G12 8QQ, UK
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Nicolaou M, Papanikolaou MG, Tsipis AC, Kabanos TA, Keramidas AD, Sproules S, Miras HN. Design and Assembly of Covalently Functionalised Polyoxofluorovanadate Molecular Hybrids. Chemistry 2018; 24:3836-3845. [PMID: 29319211 DOI: 10.1002/chem.201705730] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Indexed: 11/11/2022]
Abstract
Mixed-valent polyoxometalate (POM) clusters are one of the most interesting host species, showing a wide range of structural features and properties. The facile preparation and functionalisation of a mixed-valent polyoxofluorovanadates is reported, where two electrons are trapped to antipodal sites of the clusters. The first members of this family of clusters with the general formula, [VV12 VIV2 O16 (μ-O)10 (μ3 -O)10 (μ3 -F)2 (L)2 ]6- , where L: py=pyridine (1); pyr=pyrazine (2); im=imidazole (3), are unique organic-inorganic hybrids with the addition of a N-donor ligand at either end of the polyoxofluorovanadate. The composition and connectivity of 1-3 were characterised by single-crystal X-ray diffraction and electrospray ionisation mass spectrometry. Electron paramagnetic resonance spectroscopy revealed that the two well-separated VIV ions in each cluster are fully uncoupled with J=0, giving a degenerate singlet-triplet ground state. This attenuation of the exchange interaction is probed with density functional theoretical calculations that reveal that the inclusion of the fluoride ion in the cluster produces a bond pathway biased toward destructive interference between competing ferromagnetic and antiferromagnetic interactions. These robust molecular materials are the ideal combination of desirable electronic properties, with an organic handle with which they can be integrated into spintronic circuitry for molecular devices.
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Affiliation(s)
- Maria Nicolaou
- Department of Chemistry, University of Cyprus, 2109, Nicosia, Cyprus
| | - Michael G Papanikolaou
- Section of Inorganic and Analytical Chemistry, Department of Chemistry, University of Ioannina, 45110, Ioannina, Greece
| | - Athanassios C Tsipis
- Section of Inorganic and Analytical Chemistry, Department of Chemistry, University of Ioannina, 45110, Ioannina, Greece
| | - Themistoklis A Kabanos
- Section of Inorganic and Analytical Chemistry, Department of Chemistry, University of Ioannina, 45110, Ioannina, Greece
| | | | - Stephen Sproules
- WestCHEM, School of Chemistry, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Haralampos N Miras
- WestCHEM, School of Chemistry, University of Glasgow, Glasgow, G12 8QQ, UK
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Stösser R, Marx U, Herrmann W, Jabor JK, Brückner A. In Situ EPR Study of Chemical Reactions in Q-Band at Higher Temperatures: A Challenge for Elucidating Structure−Reactivity Relationships in Catalysis. J Am Chem Soc 2010; 132:9873-80. [DOI: 10.1021/ja1035418] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Reinhard Stösser
- Leibniz-Institut für Katalyse e. V. an der Universität Rostock, Albert-Einstein-Strasse 29a, D-18059 Rostock, Germany, Institute of Chemistry, Humboldt University of Berlin, Brook-Taylor-Strasse 2, D-12489 Berlin, Germany, and Institute of Pharmacy, Free University of Berlin, Kelchstrasse 31, D-12169 Berlin, Germany
| | - Ulrich Marx
- Leibniz-Institut für Katalyse e. V. an der Universität Rostock, Albert-Einstein-Strasse 29a, D-18059 Rostock, Germany, Institute of Chemistry, Humboldt University of Berlin, Brook-Taylor-Strasse 2, D-12489 Berlin, Germany, and Institute of Pharmacy, Free University of Berlin, Kelchstrasse 31, D-12169 Berlin, Germany
| | - Werner Herrmann
- Leibniz-Institut für Katalyse e. V. an der Universität Rostock, Albert-Einstein-Strasse 29a, D-18059 Rostock, Germany, Institute of Chemistry, Humboldt University of Berlin, Brook-Taylor-Strasse 2, D-12489 Berlin, Germany, and Institute of Pharmacy, Free University of Berlin, Kelchstrasse 31, D-12169 Berlin, Germany
| | - Jabor K. Jabor
- Leibniz-Institut für Katalyse e. V. an der Universität Rostock, Albert-Einstein-Strasse 29a, D-18059 Rostock, Germany, Institute of Chemistry, Humboldt University of Berlin, Brook-Taylor-Strasse 2, D-12489 Berlin, Germany, and Institute of Pharmacy, Free University of Berlin, Kelchstrasse 31, D-12169 Berlin, Germany
| | - Angelika Brückner
- Leibniz-Institut für Katalyse e. V. an der Universität Rostock, Albert-Einstein-Strasse 29a, D-18059 Rostock, Germany, Institute of Chemistry, Humboldt University of Berlin, Brook-Taylor-Strasse 2, D-12489 Berlin, Germany, and Institute of Pharmacy, Free University of Berlin, Kelchstrasse 31, D-12169 Berlin, Germany
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Structural evolution of H4PVMo11O40⋅xH2O during calcination and isobutane oxidation: New insights into vanadium sites by a comprehensive in situ approach. J Catal 2007. [DOI: 10.1016/j.jcat.2006.11.004] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Gutjahr M, Hoentsch J, Böttcher R, Storcheva O, Köhler K, Pöppl A. A Q- and X-band pulsed electron nuclear double resonance study of the structure and location of the vanadyl ions in the Cs salt of heteropolyacid PVMo11O40. J Am Chem Soc 2004; 126:2905-11. [PMID: 14995208 DOI: 10.1021/ja030576z] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The location and coordination geometry of vanadium(IV) ions in the cesium salt of molybdovanadophosphoric heteropolyacid Cs(4)PVMo(11)O(40) were studied using orientation-selective pulsed ENDOR (electron nuclear double resonance) experiments. To enhance the orientation selectivity for the paramagnetic vanadyl species, these investigations were done at Q-band frequencies. It was possible to resolve interactions of the paramagnetic vanadyl ions (VO(2+)) with all relevant nuclei, (1)H, (31)P, (51)V, and (133)Cs. The location of the vanadyl species was studied by determination of the complete (31)P hyperfine tensor. This approach was done for both the fresh and the calcined Cs(4)PVMo(11)O(40) materials, and no differences in the structures of the VO(2+) complexes were found. The ENDOR results give experimental evidence for the location of the V(IV) ions. For both samples, it was possible to exclude the incorporation of V(IV) at the Mo sites. The VO(2+) species are directly attached to the outer surface of the heteropolyanion and coordinated to four of the outer oxygen atoms with a V-P distance of 3.96 A.
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Affiliation(s)
- Marlen Gutjahr
- Fakultät für Physik und Geowissenschaften, Universität Leipzig, Linnéstrasse 5, D-04103 Leipzig, Germany
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Pöppl A, Manikandan P, Köhler K, Maas P, Strauch P, Böttcher R, Goldfarb D. Elucidation of structure and location of V(IV) ions in heteropolyacid catalysts H4PVMo11O40 as studied by hyperfine sublevel correlation spectroscopy and pulsed electron nuclear double resonance at W- and X-band frequencies. J Am Chem Soc 2001; 123:4577-84. [PMID: 11457244 DOI: 10.1021/ja004291n] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Electron spin resonance, pulsed electron nuclear double resonance (ENDOR) spectroscopy at W- and X-band frequencies, and hyperfine sublevel correlation (HYSCORE) spectroscopy have been employed to determine the location of the V(IV) ions in H4PVMo11O40 heteropolyacid catalysts. In these materials the heteropolyanions have the well-known structure of the Keggin molecule. Interactions of the unpaired electrons of the paramagnetic vanadyl ions (VO(2+)) with all relevant nuclei 1H, 31P, and 51V) could be resolved. The complete analysis of the hyperfine coupling tensor for the phosphorus nucleus in the fourth coordination sphere of the V(IV) ion allowed for the first time a detailed structural analysis of the paramagnetic ions in heteropolyacids in hydrated and dehydrated catalysts. The 31P and 1H ENDOR results show that V(IV) ions are incorporated as vanadyl pentaaqua complexes [VO(H2O)5](2+) in the void space between the heteropolyanions in the hydrated heteropolyacid. For the dehydrated H4PVMo11O40 materials the distance between the V(IV) ion and the central phosphorus atom of the Keggin molecule could be determined with high accuracy on the basis of orientation-selective 31P ENDOR experiments and HYSCORE spectroscopy. The results give a first direct experimental evidence that the paramagnetic vanadium species are not incorporated at molybdenum sites into the Keggin structure of H4PVMo11O40 and also do not act as bridges between two Keggin units after calcination of the catalyst. The vanadyl species are found to be directly attached to the Keggin molecules. The VO(2+) ions are coordinated to four or three outer oxygen atoms from one PVMo11 heteropolyanion in a trigonal-pyramidal or slightly distorted square-pyramidal coordination geometry, respectively.
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Affiliation(s)
- A Pöppl
- Universität Leipzig, Fakultät für Physik und Geowissenschaften, Linnéstrasse 5, D-04103 Leipzig, Germany
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Brückner A, Zanthoff HW. The structure of catalytically active vanadium sites in V–Sb oxides: an EPR study of asynthesized and tungsten promoted working catalysts. Colloids Surf A Physicochem Eng Asp 1999. [DOI: 10.1016/s0927-7757(99)00137-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Ilkenhans T, Siegert H, Schlögl R. The mechanism of the synthesis in connection with assignments for a solid reaction cycle of the HPA catalyst during catalytic reactions. Catal Today 1996. [DOI: 10.1016/s0920-5861(96)00218-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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