Mixed-ligand Lanthanide Complexes Research Articles

Studies on Electrostatic Effect and Tetrad Effect in some Mixed-ligand Lanthanide Complexes with Alizarine Red Sulphonate

Studies on Electrostatic Effect and Tetrad Effect in some Mixed-ligand Lanthanide Complexes with Alizarine Red Sulphonate

Mixed-ligand lanthanide complexes. Part VI. Electronic spectral study of some Ln(fod) 3 adducts with heterocyclic amines

The electronic spectra of Ln(fod) 3pyz complexes (where Ln stands for Pr(III), Nd(III), and Er(III) and pyz is pyrazine) in the visible region have been analysed. The band shapes and oscillator strengths of the hypersensitive transitions display pronounced changes as compared to respective aqua-ions. The band shapes of the hypersensitive transitions show remarkable changes on passing from solid to solution states which are the result of changes in the environment about the lanthanide ion in the two states and suggest coordination of a solvent molecule. A comparative account of hypersensitivity in the present complexes with those of other adducts of Ln(fod) 3 with imidazole and pyrazole is discussed.

Mixed ligand complexes of lanthanides with macrocyclic and open-chained polyamino-polycarboxylic acids and acetylacetone

Mixed ligand complexes of lanthanides with macrocyclic and open-chained polyamino-polycarboxylic acids and acetylacetone

ChemInform Abstract: Mixed Ligand Complexes of Lanthanides with Macrocyclic and Open‐chained Polyaminopolycarboxylic Acids and Acetylacetone.

AbstractIn view of the respective 7‐ and 8‐coordination capability of the ligands H2L′ and HzLz as well as the possibility of lanthanide forming higher order mixed ligand complexes for solvent extraction applications, studies of mixed ligand complex stability and kinetics using acetylacetone as the auxiliary ligand and H2L3 and EDTA for comparison purposes were carried out.

Mixed-ligand lanthanide complexes. IV. Paramagnetic shift induced by eu(fod) 3pz and Yb(fod) 3PZ in the NMR spectrum of di-l-butyl ether

Two pyrazole adducts of Ln(fod) 3, Eu(fod) 3pz and Yb(fod) 3pz have been scanned as potential NMR shift reagents using di-l-butyl ether. Di-l-butyl ether is a very weak donor; even then the complexes associate with the base and induce large isotropic hyperfine shifts in the resonance frequencies of the magnetic substrate nuclei. The t-butyl resonances of the complexes are strongly shifted (in the opposite direction) in the presence of the substrate. This observation together with the fact that the spectra of the substrate are unaffected by addition of any amount of the complexes are taken as evidence that the specific coordination of the complexes to the substrate occurs through the agency of oxygen lone-pair electrons.

Mixed-ligand lanthanide complexes. V. Paramagnetic shift induced by Yb(fod) 3pz in the NMR spectrum of benzyl alcohol

Mixed-ligand lanthanide complexes. V. Paramagnetic shift induced by Yb(fod) 3pz in the NMR spectrum of benzyl alcohol

Mixed ligand complexes of lanthanides with macrocyclic and open-chained polyaminopolycarboxylic acids and acetylacetone

Studies of mixed ligand complex formation stabilities and dissociation kinetics have been performed on lanthanide ions with macrocyclic and open- chained polyaminopolycarboxylic acids ( i.e. DAPDA, DACDA, EDDA, and EDTA) and acetylacetone (acac). From UV spectroscopic evidence, it was found that Ln(DACDA) + and Ln(EDTA) − complexes do not form mixed ligand complexes with acac under the set conditions, i.e. pH = 7.2 and complex concentration of 1 x 10 −4 M. On the other hand, formation of Ln(DAPDA)(acac) and Ln(EDDA)(acac) 2 − complexes were readily detectable. The mixed complex forma- tion constants,β 1, for the equilibrium Ln(L) + + acac − ⇌ Ln(L)(acac), and β 2, for the equilibrium Ln(L) + + 2 acac − ⇌ Ln(L)(acac) 2 − were determined by potentiometric titration technique where possible. It was found that β 1 values were in general greater for Ln(EDDA) + complexes than for Ln(DAPDA) + complexes indicating the resulting reduced charge density at the lanthanide ion of Ln(DAPDA) + and that less space is available for the acetylacetone moiety to coordinate to the Ln(DAPDA) + complexes due to the large size and the greater number of coordination atoms of DAPDA. The hydrolysis constants of Ln(EDDA)(H 2O) n + species were also determined and were found to be increasing with increasing atomic number of Ln. Attempts to measure the acid assisted mixed ligand complex dissociation rates by a stopped-flow spectrophotometer were not fruitful due to the much faster rates.

Mixed-ligand complexes of trivalent lanthanides. Part 3. Complexes of heptafluorodimethyloctane-3,5-dione and pyrazine: syntheses and spectral studies

The lanthanide(III) tris(heptafluorodimethyloctanedionates), [Ln(fod)3], form solid adducts with pyrazine (pyz) resulting in an increase in co-ordination number of the lanthanides from 6 to 7. In these adducts pyrazine co-ordinates through only one of its nitrogen atoms. The praseodymium, europium, and ytterbium adducts have been investigated for their applicability as lanthanide shift reagents. The dipolar shift produced in the spectra of butanol, benzyl alcohol, and dibutyl ether is discussed. The complexes do not dissociate even in the presence of added substrates (alcohols or ether).

Mixed-ligand lanthanide complexes—II : Complexes of β-diketone and heterocyclic amine. Synthesis and spectroscopic studies

The imidazole adducts of tris(heptafluorooctanedionato)lanthanide(III), [Ln(fod) 3 · im] have been synthesized and characterized. The electronic spectra in the visible region have been analysed and spectral parameters ( β , b 1/2, δ and T λ) and oscillator strengths calculated and discussed. These complexes are more covalent than the analogous [Ln(fod) 3 · pz] complexes, pz = pyrazole. The covalency is more in solution than in the solid state. The experimental and the calculated oscillator strengths are in good agreement. The band shape for the hypersensitive transition in the solid and solution spectra is compared with the other known systems and discussed. The difference in the band shape of the hypersensitive transition in the solid and in solution is indicative of solvent molecule coordination. The Mössbauer spectrum of [Eu(fod) 3 · im] is reported. The dipolar shift produced in the NMR spectrum of [Eu(fod) 3 · im] is upfield in comparison to the signal of the organic moiety itself as well as in its diamagnetic analogues. The coordinated base does not dissociate even in DMSO solution. Due to their poor solubility these compounds are not suitable for use as induced NMR shift reagents.

Solvent extraction studies on the mixed ligand complexes of lanthanides with antipyrine and perchlorate

Lanthanide ions are found to form colourless mixed-ligand complexes with antipyrine in presence of perchlorate at pH 4.0, and these are quantitatively extractable into nitrobenzene. The composition of the extracted species is shown to be metal:antipyrine:perchlorate = 1:6:3. The variation of the extraction constants with atomic number of the lanthanides is attributed to the “tetrad effect”.

Circularly polarized luminescence studies of mixed-ligand lanthanide complexes having the general formula Tb(pyridine-2,6-dicarboxylic acid)m(L-malic acid)n, where m = 0-3 and n = 0-2

Circularly polarized luminescence studies of mixed-ligand lanthanide complexes having the general formula Tb(pyridine-2,6-dicarboxylic acid)m(L-malic acid)n, where m = 0-3 and n = 0-2

Chemistry of lanthanons—XVIII: Mixed chelates of La, Pr, Nd, Sm and Y containing β-diketone and bis-salicylaldehyde ethylenediamine

Mixed ligand complexes of lanthanides (La, Pr, Nd, Sm) and Y containing botg β-diketone and bis-salicylaldehyde ethylenediamine (H 2 Salen) as the associated ligand molecules have been prepared. By reacting tris-acetyl acetonate and tris-propionyl acetonates of the above lanthanides with the Schiff's base in ammoniacal atmosphere compounds obtained were of the type [Ln(diket) 2(Salen) 0.5] (I), whereas by refluxing the tris-benzoyl acetonates and tris-dibenzoyl methanides with the Schiff's base, a second series of compound viz., [Ln(diket)(Salen)] (II) were obtained. Sodium salts of tetrakisbenzoyl acetonates and dibenzoyl methanides also yield compounds of the second type.