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001-es BibID:	bibEBI00008428
Első szerző:	Burai László
Cím:	Synthesis, potentiometry, and NMR studies of two new 1,7-disubstituted tetraazacyclododecanes and their complexes formed with lanthanide, alkaline earth metal, Mn2+, and Zn2+ ions / L. Burai, J. Ren, Z. Kovács, E. Brücher, A. D. Sherry
Dátum:	1998
ISSN:	0020-1669
Megjegyzések:	Two new 1,7-disubstituted-1,4,7,10-tetraazacyclododecane ligands, DO2P and DO2PME, and their complexes with Mg2+, Ca2+, Sr2+, Mn2+, Zn2+ and Ln3+ were prepared and characterized by pH potentiometry. The pH titration data showed that DO2P and DO2PME both form 1:1 M:L complexes with all divalent and trivalent metal ions. Protonated complexes did not appear to form with the bis(phosphonate ester) ligand, DO2PME, but were evident for all of the metal ion?DO2P complexes. The alkaline earth metal ion?DO2P complexes formed both ML and MHL complexes while the lanthanide ion (Ln3+), Zn2+, and Mn2+ complexes of DO2P formed ML, MHL, and MH2L species. Zn2+ formed the most stable complex with both ligands. The stability (β101) of the LnDO2PME+ complexes increased by about 2 orders of magnitude along the lanthanide series (La3+ to Lu3+) while the stability of the LnDO2P- complexes over this same series increased by over 3 orders of magnitude. The bis(phosphonate) ligand, DO2P, and some of its complexes formed with Ln3+ ions were further examined by NMR spectroscopy. 1H and 31P spectra of DO2P collected as a function of pH provided evidence that the first two protonations on the ligand take place largely at the tertiary nitrogens. The similarity of the 31P chemical shifts of EuDO2P- and EuDOTP5- indicate that DO2P forms an ?in-cage" complex with Eu3+ using all four macrocyclic ring nitrogens and the two phosphonate sidearms as ligands. 17O NMR shifts of the water signal indicated that the DyDO2P- complex has two inner-sphere coordinated water molecules. In the presence of excess of DO2P, a 1:2 metal:ligand, LnDO2P(HDO2P)4-, complex forms with the second ligand interacting only weakly with the coordination sites left vacant by the first DO2P. Both water proton relaxivity data for GdDO2P- and 31P NMR spectra of EuDO2P- provide evidence for formation of an ?out-of-cage" LnH2DO2P+ complex at low pH values (<6.5) in which the two phosphonate groups of DO2P are only involved in bonding with the lanthanide cation.
Tárgyszavak:	idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:	Inorganic Chemistry. - 37 : 1 (1998), p. 69-75. -
További szerzők:	Ren, Jimin Kovács Zoltán Brücher Ernő (1935-) (vegyész) Sherry, A. Dean
Internet cím:	DOI
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