Four novel coordination polymers of transition metals built using a semi rigid oxygen donor ligand: Crystal structures, novel topology and emission studies

Four new coordination polymers namely, [Cd-3(L-1)(2)(DMA)(4)](n) (1), [Mn(HL1)(H2O)(3)](n) (2), [Mn(H2L2)](n) (3) and {[Co-2(HL2)(L-2)]center dot(Et4N)center dot(1.5H(2)O)}(n) (4) have been synthesized with semi-rigid ether bridged tricarboxylic acid ligands H3L1 and H3L2 [H3L1 = 5-(4-carboxy-phenoxy)-isophthalic acid and H3L2 = 5-(2-carboxyphenoxy)-isophthalic acid] with various transition metal ions using hydro(solvo)thermal techniques. All the coordination polymers have been structurally characterized by IR spectroscopy, elemental analysis, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA) and X-ray single crystallography. Single crystal X-ray studies show that these coordination polymers contain homometallic clusters varying from dimeric to trimeric units except 2 which is a linear monomeric. On reacting para-isomer of the ligand H3L1 with metal ions, 2D and 3D supramolecular structures have been obtained while with the ortho-isomer H3L2 dimeric 2D and 3D framework were obtained. Topological analysis reveals that 1 and 3 are binodal (3,6)-connected kgd net, 2 is also a binodal (3,3)-connected honey-comb type hcb net, while 4 shows unprecedented (3,3,6)-connected pkb5 topological trinodal-network. Interestingly, 3 and 4 exhibits unusual coordination modes involving one of carbonyl 0 atom of an acid functional group. Moreover, in 4 ethereal 0 atom is also coordinated to one of the metal center. All complexes show high thermal stability, thus losing coordinated and lattice solvent molecules in the range, similar to 100-200 degrees C. Upon excitation at 325 nm, compounds 1-4 exhibit solid-state luminescences at room temperature. (C) 2012 Elsevier Ltd. All rights reserved,