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001-es BibID:	BIBFORM087718
Első szerző:	Szilágyi Erika
Cím:	Equilibria and formation kinetics of some cyclen derivative complexes of lanthanides / Erika Szilágyi, Éva Tóth, Zoltán Kovács, Johannes Platzek, Bernd Radüchel, Ernö Brücher
Dátum:	2000
ISSN:	0020-1693
Megjegyzések:	The kinetics of the formation reactions between the lanthanide(III) ions Ce 3+, Eu 3+ and Yb 3+ and four cyclen derivative ligands, DO3A-B, DO3A-ME, DO2A and DO2A-2B, were studied by spectrophotometry and a stopped-flow method at 25?C in 1.0 M KCl solutions. The reactions were found to be of first order, which was interpreted in terms of the formation of a diprotonated intermediate, Ln(H 2L) +. The formation of products occurs via deprotonation and rearrangement of the intermediate, characterised by the rate constant, k r. The rate law obtained, k r= k OH[OH ?], is similar to those obtained for the formation reactions of DOTA and DOTA derivative complexes. The rate constants, k OH, decrease with decrease in the number of charged carboxylate functional groups in the ligands; the lowest rates were found for the formation of the DO2A complexes. The formation rates increase significantly from Ce 3+ to Yb 3+. The direct proportionality between the formation rates and [H +] ?1 was interpreted by assuming the equilibrium formation of a monoprotonated intermediate, Ln(HL), which undergoes deprotonation in a slow, rate-determining step. The validity of general base catalysis was detected in the formation reactions, which supports the assumption of the rate-controlling role of deprotonation of the monoprotonated intermediate. The protonation constants of the ligands DO3A-ME and DO2A-2B and the stability constants of their complexes were also determined. The ligand DO2A forms the usual complexes Ln(DO2A) + and the unusual species Ln(DO2A) 2 ? . In the complexes Ln(DO2A) 2 ? , the two ligands exhibit different coordination modes which were demonstrated by 1H NMR spectroscopy.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban folyóiratcikk Stability constants Lanthanide complexes Cyclen complexes
Megjelenés:	Inorganica Chimica Acta. - 298 : 2 (2000), p. 226-234. -
További szerzők:	Tóth Éva (1960-) (kémikus) Kovács Zoltán Platzek, Johannes Radüchel, Bernd Brücher Ernő (1935-) (vegyész)
Pályázati támogatás:	T 025462 OTKA
Internet cím:	Szerző által megadott URL DOI Intézményi repozitóriumban (DEA) tárolt változat
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