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001-es BibID:	BIBFORM087688
Első szerző:	Bodor Andrea
Cím:	19F NMR Study of the Equilibria and Dynamics of the Al3+/F- System / A. Bodor, I. Tóth, I. Bányai, Z. Szabó, G. T. Hefter
Dátum:	2000
ISSN:	0020-1669 1520-510X
Megjegyzések:	A careful reinvestigation by high-field 19F NMR (470 MHz) spectroscopy has been made of the Al3+/F- system in aqueous solution under carefully controlled conditions of pH, concentration, ionic strength (I), and temperature. The 19F NMR spectra show five distinct signals at 278 K and I ) 0.6 M (TMACl) which have been attributed to the complexes AlFi(3-i)+(aq) with i e 5. There was no need to invoke AlFi(OH)j(3-i-j)+ mixed complexes in the model under our experimental conditions (pH e 6.5), nor was any evidence obtained for the formation of AlF63-(aq) at very high ratios of F-/Al3+. The stepwise equilibrium constants obtained for the complexes by integration of the 19F signals are in good agreement with literature data given the differences in medium and temperature. In I ) 0.6 M TMACl at 278 K and in I ) 3 M KCl at 298 K the log Ki values are 6.42, 5.41, 3.99, 2.50, and 0.84 (for species i ) 1-5) and 6.35, 5.25, and 4.11 (for species i ) 1-3), respectively. Disappearance of the 19F NMR signals under certain conditions was shown to be due to precipitation. Certain 19F NMR signals exhibit temperature- and concentration-dependent exchange broadening. Detailed line shape analysis of the spectra and magnetization transfer measurements indicate that the kinetics are dominated by F- exchange rather than complex formation. The detected reactions and their rate constants are AlF22+ + F- h AlFF2+ + F- (k02 ) (1.8 ( 0.3) ? 106 M-1 s-1), AlF30 + F- h AlF2F0 + F- (k03 ) (3.9 ( 0.9) ? 106 M-1 s-1), and AlF30 + HF h AlF2F0 + HF (kH03 ) (6.6 ( 0.5)?104 M-1 s-1). The rates of these exchange reactions increase markedly with increasing F- substitution. Thus, the reactions of AlF2+(aq) were too inert to be detected even on the T1 NMR time scale, while some of the reactions of AlF30(aq) were fast, causing large line broadening. The ligand exchange appears to follow an associative interchange mechanism. The cis-trans isomerization of AlF2+(aq), consistent with octahedral geometry for that complex, is slowed sufficiently to be observed at temperatures around 270 K. Difference between the Al3+/F- system and the much studied Al3+/OH- system are briefly commented on.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban folyóiratcikk
Megjelenés:	Inorganic Chemistry. - 39 : 12 (2000), p. 2530-2537. -
További szerzők:	Tóth Imre (1950-) (vegyész) Bányai István (1953-) (vegyész) Szabó Z. Hefter, G. T.
Pályázati támogatás:	T 026115 OTKA
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001-es BibID:	BIBFORM086049
Első szerző:	Bodor Andrea
Cím:	Thallium(III) coordination compounds: chemical information from Tl-205 NMR longitudinal relaxation times / Andrea Bodor, István Bányai, Jozef Kowalewski, Julius Glaser
Dátum:	2002
ISSN:	0749-1581
Megjegyzések:	Tl-205 longitudinal relaxation rate measurements were performed on several thallium(III) complexes with the composition Tl(OH)(n)(H2O)(6-n)((3-n)+) (n = 1,2), Tl(Cl)(n)(H2O)(m-n)((3-n)+), Tl(Br)(n)(H2O)(m-n)((3-n)+) (m = 6 for n = 1-2, m = 5 for n = 3, m = 4 for n = 4), Tl(CN)n(H2O)(m-n)((3-n)+) (m = 6 for n = 1-2, m = 4 for n = 3-4) in aqueous solution, at different magnetic fields and temperatures. C-13 and D-2 isotopic labelling and 114 decoupling experiments showed that the contribution of the dipolar relaxation path is negligible. The less symmetric lower complexes (n < 4) had faster relaxation rate dominantly via chemical shift anisotropy contribution which depended on the applied magnetic field: T, values are between 20 and 100 ms at 9.4 T and the shift anisotropy is &UDelta;σ = 1000-2000 ppm. The tetrahedral complexes, n = 4, relax slower; their T-1 is longer than 1 s and the spin-rotation mechanism is probably the dominant relaxation path as showed by a temperature dependence study. In the case of the TICl4- complex, presumably a trace amount of TICl52- causes a large CSA contribution, 300 ppm. Since the geometry and the bond length for the complexes in solution are known from EXAFS data, it was possible to establish a correlation between the CSA parameter and the symmetry of the complexes. The relaxation behaviour of the Tl-bromo complexes is not in accordance with any known relaxation mechanism.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban folyóiratcikk NMR Tl-205 longitudinal relaxation aqueous solution thallium halide complexes thallium cyanide complexes
Megjelenés:	Magnetic Resonance In Chemistry. - 40 : 11 (2002), p. 716-722. -
További szerzők:	Bányai István (1953-) (vegyész) Kowalewski, Jozef Glaser, Julius
Pályázati támogatás:	T035127 OTKA
Internet cím:	Szerző által megadott URL DOI Intézményi repozitóriumban (DEA) tárolt változat
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001-es BibID:	BIBFORM085822
Első szerző:	Bodor Andrea
Cím:	1H- and 13C-NMR as tools to study aluminium coordination chemistry-aqueous Al(III)-citrate complexes / Andrea Bodor, István Bányai, Imre Tóth
Dátum:	2002
ISSN:	0010-8545
Megjegyzések:	Based on the use thermodynamic and solid state structure data, 1H- and 13C-NMR is a very useful tool to understand the conformational and dynamic behavior of complexes containing organic ligands in solution. In this paper we describe shortly the possibilities of the assignation of the spectra by means of modern NMR techniques. From the assigned spectra the scalar and dipolar couplings make it possible to determine the orientation of the ligand around the metal ion and the distances between hydrogen atoms in space. Aluminium?citrate complexes are reviewed as examples. It is shown that with the armory of correlation NMR spectroscopy unique insight can be obtained in the behavior of Al?citrate species even if oligomers are present in the solution.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban folyóiratcikk Al(III)-citrate complexes Aluminium coordination NMR spectroscopy Solution structure
Megjelenés:	Coordination Chemistry Reviews. - 228 : 2 (2002), p. 175-186. -
További szerzők:	Bányai István (1953-) (vegyész) Tóth Imre (1950-) (vegyész)
Pályázati támogatás:	T035127 OTKA T038296 OTKA
Internet cím:	Szerző által megadott URL DOI Intézményi repozitóriumban (DEA) tárolt változat
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001-es BibID:	BIBFORM085821
Első szerző:	Bodor Andrea
Cím:	Slow dynamics of aluminium-citrate complexes studied by 1H- and 13C-NMR spectroscopy / A. Bodor, I. Bánya, L. Zékány, I. Tóth
Dátum:	2002
ISSN:	0010-8545
Megjegyzések:	Inter- and intra-molecular exchange reactions of the major Al(III)-citrate (Cit) complexes have been studied under equilibrium conditions in aqueous solution by 1H- and 13C-NMR using band shape analysis and magnetization transfer methods. Rate equations and activation parameters have been evaluated from concentration, pH and temperature dependent studies. The lability with respect to ligand exchange was: . The variation in lability appears to be related to the different coordination modes of the citrate ligands in the complexes. The ligand exchange reactions show an Ia mechanism for Al(Cit)23? and Sy. These two complexes are fluxional , the intra-molecular rearrangement of Sy goes through a bond rupture mechanism. As is neither fluxional nor labile for ligand exchange, kAs?0.03 s?1 at 353 K.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban folyóiratcikk Aluminium-citrate complexes 1H- and 13C-NMR spectroscopy Ligand exchange
Megjelenés:	Coordination Chemistry Reviews. - 228 : 2 (2002), p. 163-173. -
További szerzők:	Bányai István (1953-) (vegyész) Zékány László (1948-) (vegyész) Tóth Imre (1950-) (vegyész)
Pályázati támogatás:	T 26115 OTKA T038296 OTKA
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