Die Koordinationszahl von Lanthaniden: Thermodynamik der Ln^IIIEDTA‐Mischkomplexe mit den Anionen der 8‐Hydroxychinolin‐5‐sulfonsäure, Iminodiessigsäure und Nitrilotriessigsäure

Abstract

The photoelectron spectrum (PE. spectrum) of barrelene (bicyclo[2.2.2]octatriene, 4) is recorded and the first four bands are correlated with orbitals obtained with the MINDO/Z-SCF procedure. The structural changes accompagnying the ionisation process 4 + 4+ are qualitatively derived from the features of the top-occupied ah (n) MO of 4, which shows complete a-n separation. The vibrational pattern of the corresponding PE. band 0 as well as complete energy-minimisation of the geometries of 4 and 4+ support the conclusion that 4 is a rather strained molecule. The interaction of the three n-bonds in 4 are discussed in terms of 'through-sflace' and 'through-bond' interaction with lower lying a-orbitals. I t is found that the latter is far from being negligible.In a previous note of this series [2] we reported on the interaction of the n-orbitals n, and n2 in bicyclo [2.2.2] octadiene (3), as determined by high-resolution photol)

Coordination Modes in the Formation of the Ternary Am(III), Cm(III), and Eu(III) Complexes with EDTA and NTA: TRLFS, 13C NMR, EXAFS, and Thermodynamics of the Complexation

“…The same average lifetime of 729 ± 17 μs and N H2O = 0.7 for the peaks at 580.08 and 580.21 nm indicates that the ternary complex Eu(EDTA)(NTA)(H 2 O) 4- is in equilibrium with the binary Eu(NTA) 2 (H 2 O) 3- complex. This is consistent with the previous reports on the formation the ternary complexes of lanthanides with EDTA+NTA by potentiometric titration, 1 H NMR, and absorption spectral methods. − At pcH = 11.50, the peak at 580.18 nm became a major peak and a new broad peak appeared at ∼578.80 nm. This on deconvolution resolved into three peaks at 580.21, 579.95, and 578.80 nm.…”

“…The −CH 2 carbons peak of EDTA appears as a sharp peak at 67.6 ppm, while those of NTA at 66.2 and 65.0 ppm show a significant broadening on formation of the ternary complex. The increased values of the stability constant of the ternary complex of the EDTA+NTA for 9-coordinated lanthanides (La−Gd) and a decreasing trend for eight-coordinated lanthanides (Tb−Lu) also supports two different mechanisms for the formation of the ternary complex of the lanthanides along the series . The two carboxylate carbon peaks were also observed in the 13 C NMR spectra of Y−EDTA−NTA at pcH 11.12, consistent with the CN = 8.0 for Y 3+ , (6EDTA +2NTA).…”

“…This complex has a high stability constant and is more resistant to hydrolysis than the binary complex. There are many reports on the formation of the ternary complexes of Ln(EDTA) - with ligands such as acetate (Ac), oxalate (Ox), diglycolate (Dgl), iminodiacetate (IDA), 8-hydroxyquilnoline-5-sulfonate (HQS), NTA, etc. − Studies of the formation of ternary complexes of actinides are relatively few. Those investigated include UO 2 (NTA) - and Th(NTA) + with dicarboxylates, Th(EDTA) 0 and Th(CDTA) 0 (CDTA = 1,2-cyclohexanedinitrilotetraacetate) with IDA, HQS, and salicylate (SA) etc., , Pu(HEDTA) 0 (HEDTA = N - hydroxyethylethylenediaminetriacetate) or Pu(EDTA) - with NTA, IDA or Gly (glycinate), and Pu(EDTA) 0 with Cit (citrate) and CO 3 2- (carbonate) .…”

Do Aqueous Ternary Complexes Influence the TALSPEAK Process?

“…Unfortunately, the literature is of little help in understanding the enthalpies of ternary complexation of the trivalent f-elements, as there are few data available and the reported ΔH 111 values range from modestly endothermic to moderately exothermic. [37][38][39] It is not trivial to measure ΔH 111 without knowing K 111 , and we have not been able to clearly identify signatures of M(DTPA)(Lac) 3-complexes in any of our solutions. Nevertheless, one can explore the relationship between the enthalpy and equilibrium constant that would be required to account for the observed heat in order to understand if the reported Q values are small because ΔH 111 is small.…”