Syntheses, Crystal Structures And Properties Of Metal-organic Frameworks Based On Flexible Thioether Carboxylate Ligands

It is interesting for scientists to design and synthesis MOFs using the flexibleorganic bridging ligand, because it has the synthetic advantage by using the flexibleorganic bridging ligand to obtain more innovative topology structures and moreadjustability in self-assembly reaction systems. In order to explore the structures andproperties of this class of MOFs, we got a series of MOFs coordination polymers whenselect two flexible thioether carboxylate ligands and transition-metal salts as the reactivematerials. The main contents are listed as follows:(1)4-{[(1-phenyl-1H-tetrazol-5-yl)sulfanyl]methyl}-benzoic acid (Hptmba) ligandwas synthesized, and seven metal-organic frameworks (MOFs) were hydrothermal orsolvothermal synthesized by Hptmba ligand, the transition metal salts, and differentauxiliary ligands:[Ag(ptmba)]n(1),[Co(ptmba)(py)(H2O)]n(py=pyridine)(2),[Ni(ptmba)(py)(H2O)]n(3),[Co(ptmba)2(bipy)]n(bipy=4,4-bipyridine)(4),{[Ni(ptmba)2(bipy)(H2O)2]·H2O}n(5),[Cu(ptmba)(OH)]n(6),[Cu(ptmba)2(H2O)]n(7),which were characterized by elemental analysis, IR spectroscopy, PXRD,thermogravimetric analysis (TGA) and single-crystal X-ray crystallography. Complex1is a one-dimensional silver(I) coordination polymer, which are linked by multiple π-πstacking interactions into a three dimensional supramolecular framework, and it shows astrong green luminescence. Complexes2and3are isostructural, synthesized by thereaction of Co(II)/Ni(II) ion, Hptmba and pyridine, showing a “chair-like” moleculeconformation. Moreover, the structures of complexes2and3can be stable by H-bondingand π-π stacking interactions. Due to the different coordination abilities between Co(II)and Ni(II) ions, and the flexible function of ptmbaˉligand, complexes4and5displaydifferent structures using the same reaction condition. Complexes6and7are both Cu(II)complexes, and the different structures between them are due to the different reactionconditions.(2)4,4’-(((1,3,4-thiadiazole-2,5-diyl)bis(sulfanediyl))bis(methylene))dibenzoic acid(H2tsmba) ligand was synthesized, and eight MOFs were hydrothermal or solvothermal synthesized by H2tsmba ligand, the transition-metal salts, and different auxiliary ligands:{[Zn(tsmba)(phen)]·DMF}n(phen=1,10-phenanthroline monohydrate, DMF=N,N-dimethylformamide)(8),{[Cu(tsmba)(phen)(H2O)]·H2O}n(9),{[Zn(tsmba)(bpy)]·0.25DMF}n(bpy=2,2-bipyridine)(10),{[Cu(tsmba)(bpy)(H2O)]·H2O}n(11),[Co3(μ3-OH)2(tsmba)2(bpa)]n(bpa=1,2-bis(pyridin-4-yl)ethane)(12),[Cu3(μ3-OH)2(tsmba)2(bpa)]n(13),[Co3(μ3-OH)2(tsmba)2(bpe)]n(bpe=trans-1,2-bis(4-pyridyl)ethylene)(14),[Cd(tsmba)(bpp)]n(bpp=1,3-bis(pyridin-4-yl)propane)(15), which were characterizedby elemental analysis, IR spectroscopy, PXRD, TGA and single-crystal X-raycrystallography. The structures of complexes8and9are similar, which both display a1Dzigzag chain, and the tsmba2ˉligand exhibits an “extended conformation”. Due to thedifferent coordination abilities between Zn(II) and Cu(II) ions, and the flexible functionof tsmba2ˉligand, complexes10and11display different structures which obtained by thesimilar reaction conditions. Complexes12,13and14have similar structures, which allcontain a1D metal-based chain. Complex15is synthesized by two flexible ligands, andit displays a1D double chain linked by tsmba2ˉligand with the bpp ligand linked twoCd(II) ions displaying a24-number ring structure. The fluorescent properties ofcomplexes8,10and15have been performed. And the preliminary researches of themagnetic properties in complexes12,13and14are also studies. It is interesting that themagnetic result indicates complex12may be a new example of a homospin weakferromagnetic single-chain magnet (SCM).In conclusion, fifteen kinds of MOFs coordination polymers have been obtained bythe synthesized flexible thioether carboxylate ligands and transition-metal ions. Theresults show that some complexes have a higher stability and some have also displayedthe fluorescent or magnetic properties.