Thermodynamic study of lanthanide(iii) complexes with bifunctional monophosphinic acid analogues of H₄dota and comparative kinetic study of yttrium(iii) complexes

Abstract

New bifunctional H(4)dota-like ligands with three acetic acid and one phosphinic acid pendant arms and propionate (H(5)do3ap(PrA)) or 4-aminobenzyl (H(4)do3ap(ABn)) reactive groups bound to the phosphorus atom were investigated. Potentiometric studies showed that the ligands have a similar basicity to the parent H(4)dota and the stability constants of their complexes with sodium(i) and selected lanthanide(III) ions are also similar. Formation and acid-assisted decomplexation kinetics of yttrium(III) complexes with a series of H(4)dota-like ligands (H(4)dota and its phosphinic/phosphonic acid analogues) were studied and the reactions are sensitive to a slight modification of the ligand structure. The (2-carboxyethyl)phosphinic acid derivative H(5)do3ap(PrA) and the phosphonic acid ligand H(5)do3ap form complexes faster than H(4)dota. The most kinetically inert complex is that with H(4)do3ap(ABn). Rates of complexation and decomplexation can depend on the ability to transfer proton(s) outside/inside the complex cavity and, therefore, on the hydrophobicity of the ligands. The results demonstrate that the new bifunctional ligands are suitable for labelling biomolecules with yttrium(iii) radioisotopes for utilization in nuclear medicine.

Lanthanide(III) Complexes of 4,10‐Bis(phosphonomethyl)‐1,4,7,10‐tetraazacyclododecane‐1,7‐diacetic acid (trans‐H6do2a2p) in Solution and in the Solid State: Structural Studies Along the Series

“…The analogous redistribution of protons bound to ring nitrogen atoms as a consequence of the protonation of carboxylate/phosphorus acid pendant arms has been observed for other phosphorus-containing dota derivatives. [25,36,39] The protonation constants of the title ligand were determined by potentiometry, except for the first constant, which had to be determined from a dependence of 31 P{ 1 H} NMR spectroscopic chemical shift on Àlog [H + ] under controlled conditions. The protonation constants found for H 6 L are summarised in Table 1 and are compared with the values recently published by Kµlmµn et al [24] as well as with values found in the literature for similar ligands.…”

“…A summary of the experimental crystallographic data is given in Potentiometric titrations: The stock/titration solutions of aqueous HCl ( % 0.03 m), NMe 4 OH ( % 0.2 m) and metal chlorides or nitrates used were the same as in previous studies. [36,39] Titrations were carried out in a vessel equipped with a thermostat at (25.0 AE 0.1) 8C, at ionic strength I = 0.1 m (NMe 4 Cl) and in the presence of extra HCl in the Àlog [H + ] range 1.7-11.9 (or until precipitation of a metal hydroxide) using a PHM 240 pH meter, a 2 mL ABU 900 automatic piston burette and a GK 2401B combined electrode (all Radiometer, Denmark). The initial volume was 5 mL and the concentration of the ligand was approximately 0.004 m. An inert atmosphere was ensured by constant passage of argon saturated with the solvent vapour.…”

A Triazacyclononane‐Based Bifunctional Phosphinate Ligand for the Preparation of Multimeric 68Ga Tracers for Positron Emission Tomography

“…HCl, % 0.03 m; NMe 4 OH, % 0.2 m) and metal chlorides or nitrates were the same as in previous studies; [52,53] the known amount of HCl was added to the stock…”

Synthesis and Biological Applications of Phosphinates and Derivatives

“…[219]. Methyl hypophosphite was formed in situ and was reacted directly with methyl acrylate, affording, after hydrolysis, phosphinic acid 301 in 28% yield.…”