Thermodynamic and Spectroscopic Studies of Trivalentf-element Complexation with Ethylenediamine-N,N′-di(acetylglycine)-N,N′-diacetic Acid

Abstract

The coordination behavior and thermodynamic features of complexation of trivalent lanthanides and americium by ethylenediamine-N,N'-di(acetylglycine)-N,N'-diacetic acid (EDDAG-DA) (bisamide-substituted-EDTA) were investigated by potentiometric and spectroscopic techniques. Acid dissociation constants (K(a)) and complexation constants (β) of lanthanides (except Pm) were determined by potentiometric analysis. Absorption spectroscopy was used to determine stability constants for the binding of trivalent americium and neodymium by EDDAG-DA under similar conditions. The potentiometry revealed 5 discernible protonation constants and 3 distinct metal-ligand complexes (identified as ML(-), MHL, and MH2L(+)). Time-resolved fluorescence studies of Eu-(EDDAG-DA) solutions (at varying pH) identified a constant inner-sphere hydration number of 3, suggesting that glycine functionalities contained in the amide pendant arms are not involved in metal complexation and are protonated under more acidic conditions. The thermodynamic studies identified that f-element coordination by EDDAG-DA is similar to that observed for ethylenediamine-N,N,N',N'-tetraacetic acid (EDTA). However, coordination via two amidic oxygens of EDDAG-DA lowers its trivalent f-element complex stability by roughly 3 orders of magnitude relative to EDTA.

Influence of a Pre‐organized N‐Donor Group on the Coordination of Trivalent Actinides and Lanthanides by an Aminopolycarboxylate Complexant

“…Figure shows the correlation between log β 101 for trivalent gadolinium and the total ligand acidity (Σp K a ) for aminopolycarboxylates forming five‐membered chelates upon metal coordination. Structures with variable denticity and nature of the substituents adhere to this linear relationship, including ligands recently investigated by our group . Figure shows a consistent departure from this linearity when the aminopolycarboxylate reagents contain pre‐organized motifs …”

“… Linear free‐energy correlation for log β 101 for GdL complexes with total ligand acidity (Σp K a ) for aminopolycarboxylates forming five‐membered chelates upon metal coordination. In order of increasing chelate stability, the complexants adhering to the linear relationship are: (1) nitrilotriacetate, (2) ethylenediamine‐ N , N′ ‐di(acetylglycine)‐ N , N′ ‐diacetate, (3) N ‐hydroxyethane‐ N , N′ , N′ ‐triacetate, (4) ethylenediamine‐ N , N , N′ , N′ ‐tetraacetate, (5) diethylenetriamine‐ N , N′′ ‐di(acetylglycine)‐ N , N′ , N′′ ‐triacetate, (6) N ‐butyl‐2‐acetamide‐diethylenetriamine‐ N , N′ , N′′ , N′′ ‐tetraacetic acid, (7) diethylenetriamine‐ N , N , N′ , N′′ , N′′ ‐pentaacetic acid . Rigid complexants deviating from the linear correlation are: N ‐2‐methylpicolinate‐ethylenediamine‐ N , N′ , N′ ‐triacetic acid (EDTA‐Mpic), trans ‐1,2‐diaminocyclohexane‐ N , N , N′ , N′ ‐tetraacetate (CDTA), 4‐azido‐2,6‐{[bis(ethylcarboxymethyl)amino]methyl}pyridine (Py), N , N′ ‐bis(2‐methylpicolinate)‐ethylenediamine‐ N , N′ ‐diacetic acid (H 4 octapa), and 1,4,7,10‐tetraazacyclodecane (H 4 dota) …”

On the Antibacterial Activity of Azacarboxylate Ligands: Lowered Metal Ion Affinities for Bis‐amide Derivatives of EDTA do not mean Reduced Activity

“…This procedure can be considered a complement to that reported by Heathman, in which the bis‐anhydride of EDTA is ring‐opened by the ethyl ester of glycine, followed by basic hydrolysis to afford AmGly 2 . Higher overall yields of the product were reported compared to the one‐pot approach described here, although the overall process is lengthier.…”

“…[a] Charges omitted. [b] Values averaged from data reported by Martell and Heathman at T =25 °C. [c] Data from Martell and Smith at T =25 °C and I =0.1 M. [d] .…”

Lanthanide complexes with polyaminopolycarboxylates as prospective NMR/MRI diagnostic probes: peculiarities of molecular structure, dynamics and paramagnetic properties

“…Recently, a lot Fig. 16 The structure of DTPA and novel DTPA derivatives of novel DTPA derivatives have been synthesized [155,156,157,158,159,160,161] such as DTPA-BMA (DTPAbis(methyl)-amide) and other derivatives with various alkyl or aryl groups [162][163][164][165][166][167][168][169][170] some novel macrocyclic DTPA bis(amide) derivatives [171][172][173], and derivatives with the replacement of the two terminal carboxylates of DTPA 5− with the non-ionic amide groups [174,175]. The structures of DTPA and DTPA derivatives have been shown in Fig.…”