Zn(II) and Cd(II) complexes assembled from versatile 1,2,3,5-benzenetetracarboxylic acid and chelating N-donor auxiliary coligands

Four new zinc(II) and cadmium(II) metal–organic coordination complexes with tetracarboxyl tecton and N-donor chelating ligands, namely, [Zn2(H2btec)2(bpy)2(H2O)2]·4H2O (1), [Zn4(btec)2(bpy)4(H2O)6]·2H2O (2), [Zn2(btec)(phen)H2O]·2H2O (3), and [Cd3(H2btec)2(phen)4(H2O)2]·2NO3 (4) (H4btec = 1,2,3,5-benzenetetracarboxylic acid, bpy = 2,2′-bipyridyl, phen = 1,10-phenanthroline), have been prepared and characterized by elemental analysis, IR spectra and X-ray diffraction. Bi-nuclear and tetra-nuclear complexes are being observed in complexes 1 and 2, respectively, which attribute to the different deprotonation of H4btec ligands, further leading different coordination modes. Interestingly, both octahedral and triangular prism coordination environments display in complex 2. However, when phen substituted the bpy as auxiliary coligand, a two-dimensional sheet was observed in complex 3. Interestingly, when the transition metal ion was changed into Cd(II) in complex 4, the H4btec ligands are deprotonated into H2btec2− ligand with the help of nitrate group as counter ion, the Cd(II) atoms bridged the H2btec2− ligands into a one-dimensional chain. Thermal stabilities and photoluminescent properties of complexes 1–4 have also been investigated.

Graphical abstractFour new Zn(II) and Cd(II) coordination complexes were prepared under hydrothermal methods by the reaction of 1,2,3,5-benzenetrtracarboxylic acid and corresponding metal salts with chelating 2,2′-bipyridine or 1,10-phenanthroline as auxiliary coligands. Binuclear and tetra-nuclear complexes displayed in complex 1 and 2 with the Zn(II) atoms being five or six coordinated, respectively. Both octahedral and triangular prism coordination environments demonstrated in complex 2. When the 1,10-phenanthroline substitute 2,2′-bipyridine as coligand, a two-dimensional sheet (42·6)(43·6·84·102)(4) topology displayed in complex 3. In complex 4, the Cd(II) atom acts as central atom, which being bridged into a one-dimensional chain with dimer as building units, it could be viewed as 6-connected node aggregate into pcu topology with nitrate anion and another Cd(II) atom as 2-connected spacer. The results show the great influence of chelating ligand and central atom on the coordination modes of the H4btec ligands and final supramolecular structure.Figure optionsDownload full-size imageDownload as PowerPoint slide