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

The role of succinate ions in the structure of crystals containing 262 crystallographically nonequiv- alent succinate ions and atoms off-elements A (A = U(VI), La(III), or lanthanides) is analyzed using the TOPOS-InterMol program complex. It is estimated that C4H4O42- 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 O-A 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 phi(3) or gauche phi(1)) 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.