ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Impact of ligands structure on formation of hydrophilic colloids from their Gd(III) complexes with high magnetic relaxivity

Alexey Stepanov, Gulnaz Gimazetdinova, Sofia Kleshnina, Irek Nizameev, Rustem Amirov, Svetlana Solovieva, Rinas Nagimov, Alexandra Voloshina, Anastasiya Sapunova, and Asiya Mustafina

FRC Kazan Scientific Center of RAS, Kazan, Russia

E-mail: aleksestepanov@yandex.ru

Abstract: The present paper introduces specific structure of thiacalix[4]arenes derivatives adopting 1,3-alternate conformation with alkyl-carboxyl substituents as ligands for conversion of their complexes with Gd(III) ions into hydrophilic colloids with longitudinal (r₁) and transverse relaxivities (r₂) higher than that of Gd(III)-based commercial contrast agents (r₁ = 20.53 and r₂ = 23.46 mM⁻¹ s⁻¹ at 0.47 T). pH-dependent coordination of Gd(III) ions via carboxyl substituents of the thiacalix[4]arenes is the driving force for the complex formation, while the precipitation of the complexes is the basis for the colloids formation. Tert-butyl and butyl substituents of thiacalix[4]arenes were found to be of crucial impact on the complex precipitation. The specific inner- and outer-sphere ligand environment provided by the thiacalix[4]arene ligands was revealed as the optimal for high r₁ and r₂ values of the colloids. High relaxivities along with negligible cytotoxicity open up the possibility of their further use as positive contrast agents in magnetic resonance imaging (MRI).

Keywords: Carboxylated thiacalix[4]arenes ; Longitudinal relaxivity ; Paramagnetic colloids ; Hydrophilic colloids ; Gd(III) ions 

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-018-0581-9

Chemical Papers 73 (1) 261–267 (2019)