Synthesis, structures and physical properties of mixed-ligand coordination polymers based on a V-shaped dicarboxylic ligand

Abstract

Four coordination polymers formulated as [Ni₂(hfipbb)₂(2,2′-bipy)₂(H₂O)₄] (1), [Ni(4,4′-bipy)(hfipbb)(H₂O)]·0.5DMF (2), [Ni₂(hfipbb)₂(BPE)_1.5(H₂O)(μ₂-H₂O)]·DMF·2H₂O (3) and Zn(hfipbb)(2,2′-bipy)·0.5DMF (4) (H₂hfipbb = 4,4′-(hexafluoroisopropylidene)bis(benzoic acid); 2,2′-bipy = 2,2′-bipyridine; 4,4′-bipy = 4,4-bipyridine; BPE = 1,2-di(4-pyridyl)ethane; DMF = N,N-dimethylformamide) have been synthesized under solvothermal conditions based on the V-shaped H₂hfipbb ligand and different auxiliary linear N-containing ligands. Compound 1 exhibits a three dimensional (3D) supramolecular network built from 0D rings linked through hydrogen bonds and π–π packing interactions. Compound 2 displays a 3D 3-fold interpenetrating diamond network with a point symbol of (6⁶). Compound 3 gives a double layer structure with (4⁴·6²)-sql topology built from {Ni₂} clusters bridged by BPE and hfipbb²⁻ ligands. Compound 4 is a 3D array formed by interdigitated 1D zigzag [Zn₂(hfipbb)₂]_n ribbons, in which the Zn₂(COO)₄ paddle-wheel SBUs are linked by two hfipbb²⁻ ligands. Compounds 2–4 exhibit hydrophobic properties which may have potential applications in hydrophobic materials. The temperature-dependent magnetic susceptibility study shows that compound 3 exhibits antiferromagnetism properties. The photoluminescence of 4 was studied in the solid state at room temperature, and it shows broad emission with a maximum peak at around 385 nm upon excitation at 335 nm.