Benzoazacrown compound: a highly effective chelator for therapeutic bismuth radioisotopes

Abstract

Ligand H4BATA forms highly stable complex with bismuth(iii) in 1–2 min at room temperature.

Investigating the Bismuth Complexes with Benzoazacrown Tri‐ and Tetra‐Acetates

“…An excess of chloride-ion along with fast binding of Bismuth(III) by considered ligands caused an effective hampering of cation's hydrolysis upon pH increasing and allowed to collect data for constants calculation (Table 1). The stability constants of bismuth(III) complexes with H 4 BATA were previously reported in a brief communication [11] and have been further clarified in this work, and refined values are presented in Table 1.…”

“…To unify logβ for the bismuth complexes with both ligands, we repeatedly titrated solutions of Bi 3 + with H 4 BATA over a wider pH range starting from pH 1.6 (compared to the data presented in [11] ). This experiment allowed us to refine logβ values for protonated forms of complex that affected value for BATABi À as well, which turned out to be higher by 1.4 orders than that of logβ(DOTABi À ).…”

“…Stepwise (K BiHnL ) complexation constants (in log units) of H 4 BATA (refined for wider pH range vs [11] ), H 3 BA3A, and H 4 DOTA at 25.0°C in 0.1 M KNO 3 [a] and the corresponding pBi values [a] L denotes the ligand; charges of ligand and complex species were omitted for simplicity. demonstrate that both the studied ligands have a good ability to maintain bismuth cation binding despite the different levels of logβ.…”

“…In addition QTAIM [17] analysis implemented into multiwfn package [18] for BATABi complex (Fig S2 , Table S1) has shown absence of interaction between cation and macrocyclic oxygens in contrast to BA3ABi. Furthermore regarding effectiveness of BATABi complex [11] we attempted to evaluate the changing of coordination environments of Bi 3 + in the BATABi complex at different pH by EXAFS measurements of the solutions at pH 1, 3 and 11 (Figure 6, Table 5) in addition to pH 5-5.5 discussed above. Sample at pH 1 was used as reference to show the spectrum and obtained environment of free cation in presence of Cl-and H 4 BATA.…”

“…[9,10] Additionally, we determined that the aza-18-crown-6 tetraacetate (H 4 BATA) with the same macrocycle as macropa is a candidate for the Bi 3 + cation. [11] We suggested that its high efficiency is associated with the H 4 DOTA structure: H 4 BATA seems to be an opened version of H 4 DOTA, resulting in decreased restriction inside the macrocycle compared with H 4 DOTA. Additionally, the presence of the rigid benzyl moiety in the macrocycle provides a way for bifunctionalization distanced from the cation-coordinating part.…”