Evolution of manganese–calcium cluster structures based on nitrogen and oxygen donor ligands

Abstract

Several X-ray determined structures are described of ditopic clusters based on the Mn_(m)Ca_(n) motif where m = 2, n = 2; m = 6, n = 2. A cuboid arrangement of Ca₂Mn₂O₆ is observed in three structures and they vary slightly in terms of Mn–O and Ca–O bond lengths. A “wheel and axle” like motif is observed in the final structure in which a calcium thread resides inside a Mn₆ ring. Crystal packing features are also described for the cuboid structures and subtle structural changes are discussed in the framework of supramolecular chemistry and crystal engineering.