Role of Succinate Ions in the Polymorphism of Coordination Polymers of f-Metals

Resumo

The role of succinate ions in the structure of crystals containing 262 crystallographically nonequivalent succinate ions and atoms of f-elements A (А = U(VI), La(III), or lanthanides) is analyzed using the TOPOS-InterMol program complex. It is estimated that С₄Н₄О\(_{4}^{{2 - }}\) anions can display 10 topologically different types of coordination to the atoms of metals A, acting as three- or four-dentate ligands and forming from three to eight О–А bonds. It is estimated that of the two theoretically possible types of metallacycles, succinate ions usually form tetratomic cycles. Alternative heptatomic cycles are formed by only 4 out of 262 succinate ions. It is shown the type of a di-anion’s coordination affects that of its preferable coordination (trans φ³ or gauche φ¹) in a crystal’s structure. It is estimated that a change in the type of coordination or conformation of succinate ions can determine the polymorphism of succinate-containing polymers.