Abstract. We describe a simple way to produce large quantities of solid solutions of monomer CjgN... more Abstract. We describe a simple way to produce large quantities of solid solutions of monomer CjgN in pure QQ using an electric gas discharge tube. Typical concentrations are 10~5 to 10"4 CsgN with respect to Q0. The 14N and several 13C hyperfme constants were ...
In this study, relationships between preparation conditions, structure, and activity of Pt-contai... more In this study, relationships between preparation conditions, structure, and activity of Pt-containing TiO2 photocatalysts in photoinduced reforming of glycerol for H2 production were explored. Commercial Aerolyst® TiO2 (P25) and homemade TiO2 prepared by precipitation-aging method were used as semiconductors. Pt co-catalysts were prepared by incipient wetness impregnation from aqueous solution of Pt(NH3)4(NO3)2 and activated by calcination, high temperature hydrogen, or nitrogen treatments. The chemico-physical and structural properties were evaluated by XRD, 1H MAS NMR, ESR, XPS, TG-MS and TEM. The highest H2 evolution rate was observed over P25 based samples and the H2 treatment resulted in more active samples than the other co-catalyst formation methods. In all calcined samples, reduction of Pt occurred during the photocatalytic reaction. Platinum was more easily reducible in all of the P25 supported samples compared to those obtained from the more water-retentive homemade TiO2. ...
... One can raise the question, what is the Fe(III) spectrum deconvolution good for? First of all... more ... One can raise the question, what is the Fe(III) spectrum deconvolution good for? First of all toget a general picture how the spectrum is composed from the sub-spectra: how much Fe(llI) is sited in FW and EFW environments and what are the symmetries of these sites? ...
Journal of the American Chemical Society, May 1, 2003
A series of isotropic EPR spectra recorded at various concentrations and pH (in the range 2-12) o... more A series of isotropic EPR spectra recorded at various concentrations and pH (in the range 2-12) on equilibrium systems containing copper(II) and diglycine, triglycine, or tetraglycine were analyzed. A purely mathematical method, matrix rank analysis gave the number of independent EPR-active species. Two-dimensional evaluation then resulted in the formation constants and magnetic parameters of 14 metal complexes (including microspecies) in each system. The independent paramagnetic species formed with each ligand are as follows: Cu(2+) (aqua complex), [CuLH](2+), [CuL](+), [CuLH(-1)], [CuLH(-2)](-), [CuL(2)H(2)](2+), [CuL(2)H](+), [CuL(2)], [CuL(2)H(-1)](-), and [CuL(2)H(-2)](2-). Moreover, for diglycine, the diamagnetic complex [Cu(2)L(2)H(-3)](-), and for triglycine and tetraglycine, the EPR-active species [CuLH(-3)](2-) were identified. Further, equilibria of two microspecies were demonstrated for [CuL(2)], [CuL(2)H(-1)](-), and [CuL(2)H(-2)](2-). The magnetic parameters allowed a detailed description of the coordination modes. The most important findings: (1) For the mono complexes, the in-plane sigma-bonds between copper(II) and the equatorial N donors are particularly strong when the same ligand forms several adjacent chelate rings with the participation of amino N, deprotonated peptide N(s), and the carboxylate group. (2) Structures with coupled chelate rings are likewise favored in the bis complexes. Different protonation states of the two ligands are observed in the major isomer of [CuL(2)] ((LH(-1) + LH) coordination), and in the isomers of [CuL(2)H(-2)](2-) ((LH(-2) + L) coordination) for triglycine and tetraglycine.
The reaction of metallic copper, triphenylphosphine and 1,2-naphthoquinone leads to the copper(II... more The reaction of metallic copper, triphenylphosphine and 1,2-naphthoquinone leads to the copper(II) catecholate complex bis(4-triphenylphosphoniono)(naphthalene-1,2-dioxolato)copper(II), the first molecular structure of a Schönberg adduct coordinated to a metal ion.
ABSTRACT Kollektív jelenségeket vizsgáltunk szilárdtestekben multifrekvenciás elektron spin rezon... more ABSTRACT Kollektív jelenségeket vizsgáltunk szilárdtestekben multifrekvenciás elektron spin rezonancia spektroszkópiai módszerrel. - Szupravezetők és rokon mágnesesen rendezett anyagok A ma már "klasszikusnak" számító CuO2 alapú perovszkit szupravezetőkben munkánk a az antiferromágnesség és szupravezető állapotú rendszerek határán levő anyagokra irányult. Részletesen vizsgáltuk az elektromos töltés és mágneses spinsűrüség térbeli eloszlását. - Manganit perovszkitok mágnesesen rendezett és töltésrendezett állapotai Három, szerkezetében különböző rendszert vizsgáltunk, melyeknél a legérdekesebb kérdés az elméletileg jósolt inhomogén töltéseloszlás kísérleti kimutatása volt. - Elektron delokalizáció fullerén és szénalapú nanoszerkezetekben Részletesen vizsgáltuk a C59N-nel dópolt C60 rendszert, amely a fullerén félvezetők modellje lehet. Látszólagos egyszerűsége ellenére különleges mágneses és elektromos tulajdonságokat találtunk, melyeket értelmeztünk. A szén alapú nanocsövekbe fullerén spinjelzőt töltöttünk, ami lehetűvé teszi elektromos tulajdonságainak tanulmányozását. A munkát számos külföldi laboratóriummal együttműködve végeztük. Az ESR vizsgálatokat a BME-n fejlesztett, multifrekvenciás és az MTA-KKI 2004-ben felállított Bruker típusú 9 GHz-s ESR spektrométerén végeztük. Eredményeinket neves folyóiratokban közöltük. Megszerveztük a nagyfrekvenciás ESR spektroszkópia SENTINEL Európai Hálózatának zárókonferenciáját Budapesten. | We investigated collective phenomena in solids by multifrequency electron spin resonance spectroscopy. - Superconductors and parent magnetically ordered materials In the now 'classic' CuO2 based perovskite superconductors we focused on systems on the borderline of antiferromagnetism and superconductivity. We investigated in detail the spatial distribution of magnetic spin density and charge density. - Magnetic and charge ordered states in manganite perovskites We investigated three structurally different systems for which the experimental verification of the theoretically predicted inhomogeneous charge distribution is the most interesting problem. - Electron delocalization in fullerene-based and carbon-based nanostructures We investigated in detail the C59N doped C60 system that may be regarded as a model system for fullerene semiconductors. In spite of its apparent simplicity it shows special electronic and magnetic features that were explained. We filled the carbon nanotubes with fullerene spin labels that enable the study of its electric properties. The work was accomplished in collaboration with several foreign laboratories. The ESR studies were performed on the multifrequency spectrometer built at the BUTE and the Bruker spectrometer at the Chemical Research Institute of the HAS. Results were published in well-known journals. We organized the closing conference of the SENTINEL European Network for high frequency ESR spectroscopy.
Journal of the Chemical Society, Dalton Transactions, 1992
Transition-metal co-ordination equilibria of 2 (RS)-D-galactothiazolidine-4 (R)-carboxylic acid w... more Transition-metal co-ordination equilibria of 2 (RS)-D-galactothiazolidine-4 (R)-carboxylic acid were studied by potentiometric titrations in the range pH 1.58.5. In most cases,(1, 1, 1),(1, 2, 0) and (1, 2, 0) parent complexes M p L q H r were formed, but in the cases of ...
... One can raise the question, what is the Fe(III) spectrum deconvolution good for? First of all... more ... One can raise the question, what is the Fe(III) spectrum deconvolution good for? First of all toget a general picture how the spectrum is composed from the sub-spectra: how much Fe(llI) is sited in FW and EFW environments and what are the symmetries of these sites? ...
Abstract. We describe a simple way to produce large quantities of solid solutions of monomer CjgN... more Abstract. We describe a simple way to produce large quantities of solid solutions of monomer CjgN in pure QQ using an electric gas discharge tube. Typical concentrations are 10~5 to 10"4 CsgN with respect to Q0. The 14N and several 13C hyperfme constants were ...
In this study, relationships between preparation conditions, structure, and activity of Pt-contai... more In this study, relationships between preparation conditions, structure, and activity of Pt-containing TiO2 photocatalysts in photoinduced reforming of glycerol for H2 production were explored. Commercial Aerolyst® TiO2 (P25) and homemade TiO2 prepared by precipitation-aging method were used as semiconductors. Pt co-catalysts were prepared by incipient wetness impregnation from aqueous solution of Pt(NH3)4(NO3)2 and activated by calcination, high temperature hydrogen, or nitrogen treatments. The chemico-physical and structural properties were evaluated by XRD, 1H MAS NMR, ESR, XPS, TG-MS and TEM. The highest H2 evolution rate was observed over P25 based samples and the H2 treatment resulted in more active samples than the other co-catalyst formation methods. In all calcined samples, reduction of Pt occurred during the photocatalytic reaction. Platinum was more easily reducible in all of the P25 supported samples compared to those obtained from the more water-retentive homemade TiO2. ...
... One can raise the question, what is the Fe(III) spectrum deconvolution good for? First of all... more ... One can raise the question, what is the Fe(III) spectrum deconvolution good for? First of all toget a general picture how the spectrum is composed from the sub-spectra: how much Fe(llI) is sited in FW and EFW environments and what are the symmetries of these sites? ...
Journal of the American Chemical Society, May 1, 2003
A series of isotropic EPR spectra recorded at various concentrations and pH (in the range 2-12) o... more A series of isotropic EPR spectra recorded at various concentrations and pH (in the range 2-12) on equilibrium systems containing copper(II) and diglycine, triglycine, or tetraglycine were analyzed. A purely mathematical method, matrix rank analysis gave the number of independent EPR-active species. Two-dimensional evaluation then resulted in the formation constants and magnetic parameters of 14 metal complexes (including microspecies) in each system. The independent paramagnetic species formed with each ligand are as follows: Cu(2+) (aqua complex), [CuLH](2+), [CuL](+), [CuLH(-1)], [CuLH(-2)](-), [CuL(2)H(2)](2+), [CuL(2)H](+), [CuL(2)], [CuL(2)H(-1)](-), and [CuL(2)H(-2)](2-). Moreover, for diglycine, the diamagnetic complex [Cu(2)L(2)H(-3)](-), and for triglycine and tetraglycine, the EPR-active species [CuLH(-3)](2-) were identified. Further, equilibria of two microspecies were demonstrated for [CuL(2)], [CuL(2)H(-1)](-), and [CuL(2)H(-2)](2-). The magnetic parameters allowed a detailed description of the coordination modes. The most important findings: (1) For the mono complexes, the in-plane sigma-bonds between copper(II) and the equatorial N donors are particularly strong when the same ligand forms several adjacent chelate rings with the participation of amino N, deprotonated peptide N(s), and the carboxylate group. (2) Structures with coupled chelate rings are likewise favored in the bis complexes. Different protonation states of the two ligands are observed in the major isomer of [CuL(2)] ((LH(-1) + LH) coordination), and in the isomers of [CuL(2)H(-2)](2-) ((LH(-2) + L) coordination) for triglycine and tetraglycine.
The reaction of metallic copper, triphenylphosphine and 1,2-naphthoquinone leads to the copper(II... more The reaction of metallic copper, triphenylphosphine and 1,2-naphthoquinone leads to the copper(II) catecholate complex bis(4-triphenylphosphoniono)(naphthalene-1,2-dioxolato)copper(II), the first molecular structure of a Schönberg adduct coordinated to a metal ion.
ABSTRACT Kollektív jelenségeket vizsgáltunk szilárdtestekben multifrekvenciás elektron spin rezon... more ABSTRACT Kollektív jelenségeket vizsgáltunk szilárdtestekben multifrekvenciás elektron spin rezonancia spektroszkópiai módszerrel. - Szupravezetők és rokon mágnesesen rendezett anyagok A ma már "klasszikusnak" számító CuO2 alapú perovszkit szupravezetőkben munkánk a az antiferromágnesség és szupravezető állapotú rendszerek határán levő anyagokra irányult. Részletesen vizsgáltuk az elektromos töltés és mágneses spinsűrüség térbeli eloszlását. - Manganit perovszkitok mágnesesen rendezett és töltésrendezett állapotai Három, szerkezetében különböző rendszert vizsgáltunk, melyeknél a legérdekesebb kérdés az elméletileg jósolt inhomogén töltéseloszlás kísérleti kimutatása volt. - Elektron delokalizáció fullerén és szénalapú nanoszerkezetekben Részletesen vizsgáltuk a C59N-nel dópolt C60 rendszert, amely a fullerén félvezetők modellje lehet. Látszólagos egyszerűsége ellenére különleges mágneses és elektromos tulajdonságokat találtunk, melyeket értelmeztünk. A szén alapú nanocsövekbe fullerén spinjelzőt töltöttünk, ami lehetűvé teszi elektromos tulajdonságainak tanulmányozását. A munkát számos külföldi laboratóriummal együttműködve végeztük. Az ESR vizsgálatokat a BME-n fejlesztett, multifrekvenciás és az MTA-KKI 2004-ben felállított Bruker típusú 9 GHz-s ESR spektrométerén végeztük. Eredményeinket neves folyóiratokban közöltük. Megszerveztük a nagyfrekvenciás ESR spektroszkópia SENTINEL Európai Hálózatának zárókonferenciáját Budapesten. | We investigated collective phenomena in solids by multifrequency electron spin resonance spectroscopy. - Superconductors and parent magnetically ordered materials In the now 'classic' CuO2 based perovskite superconductors we focused on systems on the borderline of antiferromagnetism and superconductivity. We investigated in detail the spatial distribution of magnetic spin density and charge density. - Magnetic and charge ordered states in manganite perovskites We investigated three structurally different systems for which the experimental verification of the theoretically predicted inhomogeneous charge distribution is the most interesting problem. - Electron delocalization in fullerene-based and carbon-based nanostructures We investigated in detail the C59N doped C60 system that may be regarded as a model system for fullerene semiconductors. In spite of its apparent simplicity it shows special electronic and magnetic features that were explained. We filled the carbon nanotubes with fullerene spin labels that enable the study of its electric properties. The work was accomplished in collaboration with several foreign laboratories. The ESR studies were performed on the multifrequency spectrometer built at the BUTE and the Bruker spectrometer at the Chemical Research Institute of the HAS. Results were published in well-known journals. We organized the closing conference of the SENTINEL European Network for high frequency ESR spectroscopy.
Journal of the Chemical Society, Dalton Transactions, 1992
Transition-metal co-ordination equilibria of 2 (RS)-D-galactothiazolidine-4 (R)-carboxylic acid w... more Transition-metal co-ordination equilibria of 2 (RS)-D-galactothiazolidine-4 (R)-carboxylic acid were studied by potentiometric titrations in the range pH 1.58.5. In most cases,(1, 1, 1),(1, 2, 0) and (1, 2, 0) parent complexes M p L q H r were formed, but in the cases of ...
... One can raise the question, what is the Fe(III) spectrum deconvolution good for? First of all... more ... One can raise the question, what is the Fe(III) spectrum deconvolution good for? First of all toget a general picture how the spectrum is composed from the sub-spectra: how much Fe(llI) is sited in FW and EFW environments and what are the symmetries of these sites? ...
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Papers by Laszlo Korecz