Towards purely inorganic clusters in medicine : biocompatible divalent cations as counterions of cobaltabis(dicarbollide) and its iodinated derivatives

Abstract

Monovalent cations, Cs+, and alkylammonium ([NR4]+) salts have traditionally been used to precipitate the anions of boranes, carborane and metallocarborane clusters. In contrast, in the body and in living organisms in general, divalent cations have a special relevance. In this work, we isolate for the first time the cobaltabis(dicarbollide) salts of the biocompatible divalent cations of biological importance that can have application both in biology and in materials science. The preparation of Ca2+, Mg2+ and Fe2+ salts of anionic iodinated nido-[C2B9H12]− and cobaltabis(dicarbollide) as well as its di-, tetra- and octa-iodinated derivatives are reported. Ca2+ and Mg2+ are hard Lewis acids and thus forms aqua ions if water is present in the synthetic process. All solid Ca2+ and Mg2+ salts studied in this work contained water molecules coordinated that have been detected by IR and TGA/DSC. Fe2+ is a medium hard Lewis acid and Fe3+ is a hard one. In acetone they do not coordinate to cobaltabis(dicarbollide) anion, but are solvated by acetone. The studied Ca2+ salts of iodinated cobaltabis(dicarbollide) are basically inorganic small molecules that provide at once the biocompatible divalent Ca2+ cation and and iodinated anions thus simultaneously providing an X-ray contrast agent and/or bone defect repairing agent in regenerative medicine.