Synthesis, structural, spectral and photoluminescent studies of new polymorphs of Ca(II) and Ba(II) complexes of diglycolic acid.

Metal carboxylates possess wide range of intriguing structural topologies due to their diverse ligational behavior of carboxylate group. Two new polymorphs of monomeric complex, [Ca(dga)(H₂O)₅].H₂O (1) and the three-dimensional metal-organic framework, [Ba(dga)(H₂O)] (2) (dgaH₂ = diglycolic acid) have been grown by gel diffusion technique at room temperature. Colourless transparent crystals were obtained within one week. Single crystal X-ray diffraction study reveals that the title compounds crystallized in monoclinic P21/n in 1 and orthorhombic system with space group Pnma in 2. The monomeric units, CaO₈ interact each other via extensive hydrogen bonding among the coordinated and the lattice water molecules with the carboxylate oxygen atoms to form a 2D supramolecular sheet like structure in 1. The adjacent BaO₈ polyhedra are connected by diglycolate ligand forming the 3D frame work with porous architecture in 2. Elemental analysis, FTIR, UV-Visible, thermogravimetric, powder X-ray diffraction and solid state photoluminescence studies were also carried out. [ABSTRACT FROM AUTHOR]