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Heterometallic Oxo-Alkoxides of Europium, Titanium and Potassium
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Coordination compounds of europium and titanium with oxide, ethoxide (OCH2CH3), iso-propoxide (OCH(CH3)2) and tert-butoxide (OC(CH3)3) ligands have been studied. These belong to the general class of oxo-alkoxides, MxOy(OR)z, with alkoxide ligands (OR) containing an organic, aliphatic part R. The R group can be systematically varied, permitting the investigation of the influence of electronic and steric effects on the coordination of metal and oxygen atoms. Their tendency towards hydrolysis and formation of metal-oxygen-metal bridges also makes (oxo)alkoxides interesting as precursors in liquid solution-based or gas phase-based synthesis of many technologically important materials.

The structure of a termetallic oxo-alkoxide of formula Eu3K3TiO2(OH/OCH3)(OR)11(HOR) (R = C(CH3)3) was revealed by a combination of single-crystal X-ray diffraction and IR spectroscopy. Its unusual structure features a facial oxygen-centered Eu3K3O octahedron sharing one face with an oxygen-centered K3TiO tetrahedron. Six-coordination of oxygen by a combination of alkali metal and lanthanoid atoms is not uncommon for alkoxides, but the attachment of a tetrahedron to one of its faces provides a new dimension to the library of oxo-alkoxide structures. The structure was the result of incomplete metathesis in the synthesis attempt of europium-titanium oxo-tert-butoxides.

Eu4TiO(OR)14 and (Eu0.5La0.5)4TiO(OR)14 (R = CH(CH3)2) were found to be isostructural with previously published Ln4TiO(OR)14 structures (Ln=Sm, Tb0.9Er0.1). X-ray diffraction and UV-Vis absorption results show no site preference for La in either the solid state or hexane solution. The Ln4TiO(OR)14 structure forms part of an interesting group of Ln4MO(OR)10+z­(HOR)q structures where M is another lanthanoid (Ln) or a di-, tri- or tetravalent heteroatom, giving either a square pyramidal or a trigonal bipyramid-like coordination of the central oxygen atom, depending on the chemistry and size of M.

Eu2Ti4O2(OR)18(HOR)2 (R = CH2CH3) was deduced from IR data to have the same molecular structure as Er2Ti4O2(OR)18(HOR)2. UV-Vis measurements are also in agreement with the presence of one symmetry-unique europium site in the molecular structure. Structure determination by single-crystal X-ray diffraction has yet to be performed.

 

Coordination compounds of europium and titanium with oxide, ethoxide (OCH2CH3), isopropoxide(OCH(CH3)2) and tert-butoxide (OC(CH3)3) ligands have been studied. Thesebelong to the general class of oxo-alkoxides, MxOy(OR)z, with alkoxide ligands (OR)containing an organic, aliphatic part R. The R group can be systematically varied, permittingthe investigation of the influence of electronic and steric effects on the coordination of metaland oxygen atoms. Their tendency towards hydrolysis and formation of metal-oxygen-metalbridges also makes (oxo)alkoxides interesting as precursors in liquid solution-based or gasphase-based synthesis of many technologically important materials.The structure of a termetallic oxo-alkoxide of formula Eu3K3TiO2(OH/OCH3)(OR)11(HOR)(R = C(CH3)3) was revealed by a combination of single-crystal X-ray diffraction and IRspectroscopy. Its unusual structure features a facial oxygen-centered Eu3K3O octahedronsharing one face with an oxygen-centered K3TiO tetrahedron. Six-coordination of oxygen bya combination of alkali metal and lanthanoid atoms is not uncommon for alkoxides, but theattachment of a tetrahedron to one of its faces provides a new dimension to the library of oxoalkoxidestructures. The structure was the result of incomplete metathesis in the synthesisattempt of europium-titanium oxo-tert-butoxides.Eu4TiO(OR)14 and (Eu0.5La0.5)4TiO(OR)14 (R = CH(CH3)2) were found to be isostructuralwith previously published Ln4TiO(OR)14 structures (Ln=Sm, Tb0.9Er0.1). X-ray diffraction andUV-Vis absorption results show no site preference for La in either the solid state or hexanesolution. The Ln4TiO(OR)14 structure forms part of an interesting group of Ln4MO(OR)10+z-(HOR)q structures where M is another lanthanoid (Ln) or a di-, tri- or tetravalent heteroatom,giving either a square pyramidal or a trigonal bipyramid-like coordination of the centraloxygen atom, depending on the chemistry and size of M.Eu2Ti4O2(OR)18(HOR)2 (R = CH2CH3) was deduced from IR data to have the samemolecular structure as Er2Ti4O2(OR)18(HOR)2. UV-Vis measurements are also in agreementwith the presence of one symmetry-unique europium site in the molecular structure. Structuredetermination by single-crystal X-ray diffraction has yet to be performed.

Place, publisher, year, edition, pages
Uppsala: Uppsala universitet, Institutionen för materialkemi , 2010. , p. 31
Keywords [en]
Alkoxides, Europium, Lanthanoids, Electronic absorption spectroscopy, f-f spectroscopy
National Category
Inorganic Chemistry
Research subject
Inorganic Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-121653OAI: oai:DiVA.org:uu-121653DiVA, id: diva2:306075
Presentation
2010-03-30, Polhemsalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2010-03-26 Created: 2010-03-26 Last updated: 2010-03-29Bibliographically approved
List of papers
1. Structure of Eu4TiO(OCH(CH3)2)14 and Eu2La2TiO(OCH(CH3)2)14 and spectroscopic studies of three Eu-Ti alkoxides: Eu4TiO(OCH(CH3)2)14, Eu2La2TiO(OCH(CH3)2)14 and Eu2Ti4O2(OC2H5)18(HOC2H5)2
Open this publication in new window or tab >>Structure of Eu4TiO(OCH(CH3)2)14 and Eu2La2TiO(OCH(CH3)2)14 and spectroscopic studies of three Eu-Ti alkoxides: Eu4TiO(OCH(CH3)2)14, Eu2La2TiO(OCH(CH3)2)14 and Eu2Ti4O2(OC2H5)18(HOC2H5)2
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Three Eu-Ti alkoxides have been synthesised and spectroscopically and structurally characterised: Eu4TiO(OCH(CH3)2)14 (1), Eu2La2TiO(OCH(CH3)2)14 (2) and Eu2Ti4O2(OC2H5)18(HOC2H5)2 (3). The structures of 1 and 2 were refined from single-crystal X-ray diffraction data. The iso-structural 1 and 2 are of the Sm4TiO(OR)14 structure type, where the La3+ and Eu3+ ions in 2 are randomly distributed over the two six-coordinated Ln positions. Electronic absorption spectroscopy shows that Eu3+ occupies both sites in solutions of 1 and 2, but differences in the fine structures of the Eu3+ f-f transition peaks due to the substitution of La3+ for Eu3+ are reported. The structure of Eu2Ti4O2(OC2H5)18(HOC2H5)2  was inferred from vibrational and electronic spectroscopic studies and comparison with the structurally determined iso-structural Er2Ti4O2(OC2H5)18(HOC2H5)2.

Keywords
Alkoxides, crystal structure, f-f spectroscopy
National Category
Inorganic Chemistry
Research subject
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-121575 (URN)
Available from: 2010-03-25 Created: 2010-03-25 Last updated: 2010-03-26
2. Structure of a hepta-nuclear termetallic oxo-alkoxide: Eu3K3TiO2(OBut)11(OMe/OH)(HOBut)
Open this publication in new window or tab >>Structure of a hepta-nuclear termetallic oxo-alkoxide: Eu3K3TiO2(OBut)11(OMe/OH)(HOBut)
2010 (English)In: Journal of Sol-Gel Science and Technology, ISSN 0928-0707, E-ISSN 1573-4846, Vol. 53, no 3, p. 681-688Article in journal (Refereed) Published
Abstract [en]

The novel termetallic oxo-methoxo-tert-butoxide Eu3K3TiO2(OBut)11(OMe/OH)(HOBut) (1) has been synthesised and structurally and spectroscopically characterised. Its unusual structure features an Eu3K3O fac-octahedron, capped by a distorted K3TiO tetrahedron on the K3 face. The compound, crystallising in space group P21/n with cell parameters a = 14.44 Å, b = 23.58 Å, c = 21.27 Å and β = 96.18°, is the result of incomplete metathesis between EuCl3 and potassium and titanium tert-butoxides in combination with deliberate hydrolysis and decomposition. It provides one of few examples of termetallic lanthanide alkoxides, as well as of an alkoxide tert-butyl group decomposing into a methyl group.

Keywords
Precursor chemistry, Oxo-alkoxide, Crystal structure, Alkoxide, Sol-gel precursor, Europium, Termetallic alkoxide, Structure
National Category
Inorganic Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-121631 (URN)10.1007/s10971-010-2150-8 (DOI)000275161100027 ()
Available from: 2010-03-26 Created: 2010-03-26 Last updated: 2017-12-12Bibliographically approved

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