Exploring cyclic aminopolycarboxylate ligands for Sb(III) complexation: PCTA and its derivatives as promising solution

Tóth-Molnár, Enikő and Lihi, Norbert and Gál, Tamás Gy. and De, Sourav and Bombicz, Petra and Bányai, István and Szikra, Dezső and Dénes, Eleonóra and Tircsó, Gyula and Tóth, Imre and Kálmán, Ferenc K. (2021) Exploring cyclic aminopolycarboxylate ligands for Sb(III) complexation: PCTA and its derivatives as promising solution. INORGANIC CHEMISTRY, 60 (18). pp. 14253-14262. ISSN 0020-1669

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Abstract

In the recent years the Auger electron emitters have been suggested as promising candidates for side effect free radiotherapy in cancer treatment. In this work we report a detailed coordination chemistry study on [Sb(PCTA)] (PCTA: 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3,6,9-triacetic acid), a macrocyclic aminopolycarboxylate type complex of antimony(III), whose 119Sb isotope could be a suitable low-energy electron emitter for radiotherapy. The thermodynamic stability of the chelate obtained by pH-potentiometry and UV-vis spectrophotometry is high enough (logK[Sb(PCTA)] = 23.2(1)) to prevent the hydrolysis of metal ion near physiological pH. The formation of [Sb(PCTA)] is confirmed by NMR and ESI-MS measurements in solution, furthermore the structure of [Sb(PCTA)]·NaCl·3H2O and [Sb(PCTA)]·HCl·3H2O is described by X-ray diffraction and DFT calculations. Consequently, the [Sb(PCTA)] is the first thermodynamically stable antimony(III) complex bearing polyamino-polycarboxylate macrocyclic platform. Our results demonstrate the potential of rigid (pyclen derivative) ligands as chelators for future application of Sb(III) in the targeted radiotherapy based on 119Sb isotope.

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