Efficient phase transfer of pertechnetate with bicyclic guanidinium compounds

Abstract

Extraction of pertechnetate with bicyclic guanidinium compounds has been studied in the KTcO4-buffer-H20/ligand-trichloromethane system Extraction data of guanidinium ligands have been compared with trialkylmethylammonium (Aliquat 336), tetraphenylphosphonium and tetraphenylarsonium chloride. The lipophilicity of extractants investigated was determined by RP-HPLC. The efficiency of pertechnetate extraction correlates with the lipophilicity of the guanidinium compounds. 1:1 complex formation in the organic phase was observed. The influence of hydroxide, chloride and bicarbonate on the pertechnetate extraction has been investigated. Pertechnetate is extracted with great preference over OH-, CI-and HCO3-, ions.

Molecular recognition of pertechnetate and perrhenate

“…48 Schmidtchen and co-workers showed that the efficiency of pertechnetate extraction correlates with lipophilicity, at least in the case of the positively charged guanidinium receptors 9-12. 19 The lipophilicity was determined from RP-HPLC analyses. Receptor 12 with phenyl substituents showed the highest lipophilicity value (i.e., even higher than tetraphenylarsonium and tetraphenylphosphonium chloride; see Table 2).…”

“…This is a concept that was first proposed by Stephan, Vo¨gtle and Schmidtchen in 1999 in the context of their work on charged organic chelators. 19,20 Unfortunately, to date it has yet to be effectively realized.…”

“…In an effort to increase the selectivity of their metal-based receptors, the Pe´rez group prepared rhenium complexes containing three 3,5-dimethylpyrazole substituents (19); this motif establishes three hydrogen bond NH sites and is designed to provide for Coulombic-based anion-receptor interactions at the same time. 53 The distinctive feature of these ligands is the fac geometry of the H-donor motifs.…”

Lipophilic urea-functionalized dendrimers as efficient carriers for oxyanions†‡

“…We are especially interested in the efficient binding of the tetrahedral oxoanion pertechnetate as a new approach to labelling organic compounds. 3 In this context dendrimers are desired having a hydrophobic periphery in order to shield the anion from hydrophilic attack. A convenient way to obtain this is reaction of the primary amino groups with alkyl and aryl isocyanates giving lipophilic polyurea-functionalized dendrimers.…”

Macrocyclic receptor for pertechnetate and perrhenate anions

“…Appropriate receptors might also permit new approaches for the radiolabeling of organic compounds without the need for the classic reduction steps involving conversion of Re(VII) and Tc(VII) to easier-to-manipulate oxidations states. 12, 13 To date, positively charged receptors have proved to be the most efficient for perrhenate and pertechnetate recognition. 7,14- 19 However, neutral receptors are promising in the sense that they may display higher binding selectivities for the targeted anions.…”