SCHEDULED MAINTENANCE
Synthesis, structures and properties of nickel(ii) and cobalt(ii) metal–organic frameworks based on a flexible tricarboxylate ligand H3TTG and different pyridyl-containing ligands†
Abstract
Along with our recent investigations on Ni and Co coordination frameworks of a flexible tripodal ligand of H3TTG (N,N′,N″-1,3,5-triazine-2,4,6-triyltris-glycine), four new complexes {[Ni(HTTG)(4,4′-bpy)(H2O)3]·(H2O)2}n (1), {[Ni2(HTTG)2(bpe)2(H2O)]·(H2O)6}n (2), {[Co2(HTTG)2(bpe)2(H2O)]·(H2O)6}n (3) and {[Co3(TTG)2(bpe)2]·(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 pyridyl-containing coligands, these complexes exhibit structural and dimensional diversity. Complex 1 shows a unique 1D chain bridged by the R22(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 Schläfli symbol (42,622,7,83)(4,62)2 based on secondary building units (SBUs) of linear cobalt clusters [Co3(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.
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