A series of 1-D, 2-D and 3-D coordination polymers self-assembled from a flexible dicarboxylate and mixed N-donor ligands: syntheses, structural diversity, and luminescent properties

Abstract

We have synthesized a series of metal–organic coordination frameworks under solvothermal conditions, formulated as [Cu(L)(phen)](1), [Co₂(L)₂(bib)]·CH₃OH(2), [Co(L)(btmb)_0.5](3), [Zn(L)(bib)]·2H₂O(4), [Cu(L)(bib)]·DMF(5), and [Mn₄(L)₄(bimb)(CH₃OH)](6) based on a flexible multicarboxylic bridging ligand 4,4′-methylenebis(oxy)-dibenzoic acid (H₂L) and flexible N-donor ligands 1,4-bis (1H-imidazol-1-yl)-butane (bib), 1,4-bis(1H-1,2,4-triazol- 1-ylmethyl)benzene (btmb), and 1,4-bis(1H-imidazol-1-ylmethyl)benzene (bimb). The structures of the frameworks have been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, and thermogravimetric analyses. The crystal structure determinations reveal that 1 has a 1-D Z-shape chain. Compounds 2 and 3 are 2-D twofold parallel interpenetrating 4-connected net with the Schläfli symbol {4⁴·6²}. Compound 4 is a 2-D threefold parallel interpenetrating 4-connected nets with the Schläfli symbol {4⁴·6²}. Compound 5 is 3-D 4-connected net with the Schläfli symbol {6⁵·8}. Compound 6 is characterized by a three-dimensional framework with one-dimensional homogeneous Mn-carboxylate chain. We found that flexible carboxylate ligands have different coordination modes under different synthetic conditions. The flexible skeleton of ligands and the coordination angle between the ligand and the metal ion is described. The luminescence and thermogravimetric properties of these compounds have been investigated.

Keywords:

• Dicarboxylate acid
• coordination polymer
• crystal structure
• interpenetration
• fluorescence