The effect of introducing of a halogen substituent into the structure of 2,2'-bipyridyl-6,6-dicarboxamide on the stability of their europium complexes has been studied. It is shown that, regardless of the size of the halogen atom, one complex particle is formed, and the metal-ligand stoichiometry of the complex is 1:1. The stability constants of europium complexes have been determined. A decrease in the size of the halogen atom leads to an increase in the stability of the complexes due to steric hindrance diminishing.
The influence of the introduction of chlorine atoms into the phenanthroline fragment of 2,9-phenanthrolinedicarboxamide on the stability constant of the europium complex has been studied. Only one complex particle is formed, and the stoichiometry of the metal-ligand complex is 1:1, regardless of the presence of acceptor substituent in the ligand structure. Presence of two chlorine substituents in the dicarboxamide leads to an increase in the stability constant of the europium complex by two orders of magnitude compared to the unsubstituted ligand.
The effect of a donor methyl groups in the structure of 6,6′-bis(di(3,5-R-phenylphosphinoyl)-2,2′-bipyridyl R = H or Me on the stability constants of lanthanum complexes was studied. Regardless of the presence of a donor substituent in phosphine oxide moiety, the stoichiometry of the complex with lanthanum was 1:1 metal to ligand. The values of the stability constant of the complexes were obtained. The insertion of methyl groups lead to increase in stability of the corresponding complexes with lanthanum which correlates well with enhance in extraction ability of the corresponding compounds towards europium.
The influence of the structure of phosphonic acid esters on the stability of their terbium complexes was studied. It was shown that one complex particle was formed irrespective the nature of the side ester chain, and the metal-ligand stoichiometry of the complex was 1:1. The stability constants of the terbium complexes were determined. An increase in the size of the bulky substituent leads to an increase in the stability of the complexes.
Here we report the investigation of complexation between lanthanide ions nitrates and 4,7-dichloro-1,10-phenanthroline- 2,9-dicarboxamide by spectrophoitometric titration technique. In all studied systems, one complex species is formed with a metal-ligand stoichiometry of 1:1. The stability of the corresponding complexes are strongly depends on the metal ion radius. All of the complexes under the study have high stability, Lu and Gd complexes possesses lgβ more than 6 and Ho and Eu – more than 7.
For the first time we study the stability of the lanthanide complexes with polydentate hyterocyclic phosphine oxides. Here we report the influence of the structure of phenanthroline (PhenPPO) and 2,2’-bipyridine (DPPO) phosphine oxides on the stability of their lanthanide complexes. An increase in the flexibility of the phosphine oxide structure leads to an increase in the stability of the complexes. The maximum of stability of the complexes is observed on neodymium ion, regardless of the structure of the ligands DPPO and PhenPPO.
The influence of structure of the phosphine oxide ligands on stability of their complexes was studied by spectroscopic techniques. Surprising the electron donating methyl groups at phenyl rings of phosphine oxide groups lead to decrease of the stability of europium complex comparing with ubsubsituted one due to their sterical prevention of conjugation between phenyl rings and P=O-groups.. This unusual behavior was first time demonstrated by spectroscopic titration and Job’s plot analysis.
The influence of the water on the stability of complexes of 6,6′-Bis(diphenylphosphinoyl)-2,2′-bipyridyl with lanthanide ions was studied. An increase in the stability value of the complexes is observed with a decrease in the ionic radius of the metal. An increasing of the water content in acetonitrile leads to decrease the stability of the complexes. Moreover the stability of the complexes became independent on ionic radii of metals.
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