Nitrilotriacetate Complex of Univalent Astatine

Abstract

Formation of the complex of the Univalent astatine cation with nitrilotriacetic acid (AtL)^^ and its stability constant (lgA^i = 8.97(4). 25 C, fi = 0.1) have been found experimentally for the first time. The complex is stable in Perchlorate solutions in presence of 5 • 10"' mol • 1"' of the oxidizer Na2S208 in the interval 4 < pH <8.5. The complex is supposed to be destroyed in weak alkaline solutions by reduction of astatine to astatide. The deprotonation constant of hypoastatic acid pA^dp = 5.23(9) was found to be lower than determined previously.The investigation was carried out by the method of ion electrophoresis in free electrolyte solutions.

Investigation of Astatine(III) Hydrolyzed Species: Experiments and Relativistic Calculations

“…The corresponding hydrolysis constants are close (Table ). The weighted average value obtained in this work, 10 –1.9 (μ=0 M), appears in fairly good agreement with the one determined by Milanov et al (10 –1.5 M –1 , μ=0.4 M) but much higher than those proposed by Schumann et al (10 –5.23 M –1 , μ=0.1 M) and Hung et al (10 –4.1 M –1 , μ=0.25 M). − …”

“…It has been shown by electromigration in noncomplexing medium (H/NaClO 4 ) that AtO + reacts with water above pH 1. ,− The mobility of the species decreases when the pH increases until it equals 0 above pH 6. Milanov and co-workers proposed the formation of a neutral hydrolyzed species AtO(OH) with an apparent hydrolysis constant of 10 –1.5 M –1 (at ionic strength μ = 0.4 M) and 10 –4.1 M –1 (at μ = 0.25 M). , A constant of 10 –5.23 M –1 (μ = 0.1 M) was also proposed by Schumann et al for the pH range of 1–10 using migration data in the presence of nitrilotriacetic acid and nitroacetate . In conclusion, though authors agree with the formation of a hydrolysis species, significant discrepancies exist between the different constants obtained.…”

“…14,15 A constant of 10 −5.23 M −1 (μ = 0.1 M) was also proposed by Schumann et al for the pH range of 1−10 using migration data in the presence of nitrilotriacetic acid and nitroacetate. 16 In conclusion, though authors agree with the formation of a hydrolysis species, significant discrepancies exist between the different constants obtained. This article aims at completing published data to provide indisputable evidence of AtO + reactivity with water using a multidisciplinary chemical approach.…”

“…The hydrolysis of AtO + is described by the following equilibrium: AtO + + m normalH 2 normalO ⇌ K hyd , m AtO false( OH false) m 1 − m + m normalH + with K hyd,m the hydrolysis constant. High-performance ion-exchange chromatography (HPIEC) coupled to a gamma detector was first used to assess the charge of the species using the approaches followed by Khalkin et al and some of us. ,, Second, the competition method proposed by Champion et al was used to define the nature of the species formed and to quantify its formation as well. Finally, the theoretical approach developed by some of us was used to evaluate the reliability of the experimental data.…”

Production of [211At]-Astatinated Radiopharmaceuticals and Applications in Targeted α-Particle Therapy

“…The metalloid-like behavior of astatine led Milesz et al to study well-known chelating agents for the sequestration of metals such as EDTA, 34 DTPA, 35 or NTA 36 (Fig. 5).…”