Interaction of [Ln(DO2A)(H2O)2-3]+ and [Ln(DO2P)(H2O)2-3]- with phosphate, acetate and fluoride anions in aqueous solution

• Autor(a) principal: Kimpe, K.
• Data de Publicação: 2001
• Outros Autores: d'Olieslager, W., Görller-Walrand, C., Figueirinha, A., Kovács, Z., Geraldes, C. F. G. C.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• DOI: 10.1016/S0925-8388(01)01154-9
• Texto Completo: http://hdl.handle.net/10316/5209; https://doi.org/10.1016/S0925-8388(01)01154-9
• topic: Nuclear resonances; Lanthanides; Rare earths; MRI contrast agents

Mixed complexation of the lanthanide(III) chelates of the 1,7-disubstituted tetraazacyclododecane macrocycles DO2A and DO2P with phosphate, acetate and fluoride anions was studied in aqueous solutions using high resolution 1H and 31P NMR spectroscopy. The [La(DO2A)(H2O)2-3]+ and [Ce(DO2A)(H2O)2-3]+ chelates readily decompose in aqueous solutions containing phosphate anions. [Nd(DO2A)(H2O)2-3]+ and [Eu(DO2A)(H2O)2-3]+ chelates remain stable in an acetate environment. Association constants for the 1:1 adduct were obtained via 1H NMR titrations. In a fluoride environment, [La(DO2A)(H2O)2-3]+ was found to be unstable, in contrast to [Eu(DO2A)(H2O)2-3]+, for which the association constant for the 1:1 adduct was calculated. Chelate formation, as well as mixed complexation with fluoride and phosphate was studied for [Eu(DO2P)(H2O)2-3]-. The 31P chemical shifts of [Eu(DO2P)(H2O)2-3]- indicate that the DO2P macrocycle forms an [`]in-cage' complex with binding through all four nitrogens. The [Eu(DO2P)(H2O)2-3]- chelate gradually decomposes in a phosphate environment, but remains stable in an fluoride environment.