Synthesis, structures and properties of nickel(II) and cobalt(II) metal organic frameworks based on a flexible tricarboxylate ligand H(3)TTG and different pyridyl-containing ligands

Along with our recent investigations on Ni and Co coordination frameworks of a flexible tripodal ligand of H(3)TTG (N, N', N-1,3,5-triazine-2,4,6-triyltris-glycine), four new complexes {[ Ni(HTTG)(4,4'-bpy)(H2O) 3]center dot(H2O)(2)}(n) (1), {[Ni-2(HTTG)(2)(bpe)(2)(H2O)]center dot(H2O)(6)} n (2), {[Co-2(HTTG)(2)(bpe)(2)(H2O)]center dot(H2O)(6)}(n) (3) and {[ Co-3(TTG)(2)(bpe)(2)]center dot(H2O)(2)} n (4) were hydrothermally synthesized through reactions of this ligand with different pyridyl-containing ligands {4,4'-bpy (4,4-bipyridine), bpe [ 1,2-bi(4-pyridyl) ethane]}, respectively. Due to various coordination modes and conformations of the flexible tricarboxylate ligand and pyridylcontaining coligands, these complexes exhibit structural and dimensional diversity. Complex 1 shows a unique 1D chain bridged by the R-2(2)(8) hydrogen bonds between the carboxylate groups, the triazine rings, and hydrogen-bonded networks of the solvent water molecules as well. Complexes 2 and 3 are isomorphous and both exhibit special 2D (8,2)-connected double-layer structures with two kinds of 1D channels constructed by the coordination bonds and hydrogen bonding interactions, respectively. Complex 4 features a 3-D network with scarce (8,3)-connected rutile-related topology with a Schla fli symbol (4 2,6 22,7,8 3)(4,6 2) 2 based on secondary building units (SBUs) of linear cobalt clusters [Co-3(CO2)(4)](2-). Significantly, with increasing flexibility of the pyridyl-containing coligands, these corresponding complexes become more and more complicated. In addition, their physical properties such as thermal, XPRD, and magnetism have also been investigated.