| Metal-Organic Frameworks?MOFs?have received enormous attention and rapid progress because of their potential applications in gas adsorption,fluorescent sensing,nonlinear optics,catalysis and magnetism.Rational design of suitable organic building blocks and metal centers to obtain functional MOFs has become the research focuses of chemical workers in current decades.In this work,three mono-,di-and tri?phenolic?carboxylic acids have been selected as the organic building blocks.Based upon these ligands,a series of MOFs were obtained through reactions with transition metals or rare-earth metals under solvothermal conditions.The research includes:1.Thirteen compounds were obtained through the reactions of 5-?2'-carboxyl phenoxy?isophtalic acid?H3L1?with d10 and lanthanide salts: [Zn?HL1??bpy?]n?1?,{[Zn2?L1??bpp???-OH??H2O?]·H2O}n?2?,[Zn1.5?L1??bpp?0.5]n?3?,[Cd?L1??Hbpp?]n?4?,[Cd1.5?L1??bpp??DMF??H2O?]n?5?,{[Ln?L1??DMF??H2O?]·DMF}n?Ln = Pr 6,Nd 7,Sm 8,Eu 9,Gd 10,Tb 11,Dy 12?and {[Eu?L1??DEF??H2O?]·2H2O}n?13??bpy = 4,4'-bipyridine,bpp = 1,3-di?pyrid-4-yl?propane?.In compound 1,carboxylic acid ligands bridge Zn atoms to give 1D?one-dimensional?zigzag chains,which were linked further by bpy ligands to form 2D?two-dimensional?undulating bilayer structure.The whole structure can be regarded as 4-connected?44?topology.Compound 2 displays a 2-D structure,in which the carboxylic acid ligands connect Zn atoms to form double metal-carboxylate chains.Bpp ligands link the adjacent chains to result into a?3,5?-connected?42.6??42.67.8?topology.Compound 3 features a 3-D?three-dimensional?double interpenetrating structure.The carboxylic acid ligands link Zn atoms to form a 2-D metal-carboxylic layer.Bpp ligands connect these layers to give the?3,4,6?-connected?4.62??66??42.68.84.10?topology.Interestingly,bpp ligands connect Zn atoms,forming right-and left-handed helical chains,which are arranged alternately within the framework.Compound 4 possesses a 3-D framework with a 3-connected 103 topology.The nanosized channels formed through the connection of Cd atoms and carboxylate ligands were occupied by monodentate coordinated bpp molecules.Compound 5 is a 2-D double layer structure.The carboxylic acid ligands connect Cd atoms,forming 1D chain with metal-carboxylate-metal arrangement.Bpp ligands further connect these chains to give rise to a 2-D double layer structure,which exhibit a?3,3,4?-connected?62.8?2?62.84?topology.Compounds 6-12 are isostructural.They all contain dimeric [Ln2?CO2?4] SBUs,which were connected thorugh carboxylic acid ligands to form a?3,6?-connected?43?2?46.66.83?topology.Compound 13 is similar to above structures,with the difference of DEF instead of DMF molecules in compound 9.Compound 1 exhibited an emission peak at 433 nm in the solid state at room temperature.Studies indicated that its fluorescence intensity in aqueous solutions is strongly correlated with the pH value and it could act as a candidate material for pH sensor.Compounds 3 and 5 display strong peaks at 354 and 336 nm,respectively,the small organic molecules have a large impact on their fluorescence properties.Compounds 9,11 and 13 at solid state emitted characteristic peaks of Eu3+ and Tb3+ ions,respectively.Both complexes can sensitively and selectively detect NB and Cu2+ ions.The quenching constants of NB are 1.6×106,1.8×107 and 5.3×106 M-1,respectively.The detection limits are 68.23,50.47 and 92.04 ppm,respectively.Magnetic measurement revealed that the-?Sm of complex 10 is 25.2 J kg-1 K-1 at 2 K for ?H of 70 k G,indicating that this compound may be a new molecular magnetic cooler.When a static dc field of 2000 Oe was applied,out-of-phase signal of compound 12 was enhanced and significant frequency-dependent out-of-phase signals with peaks were found.2.Fourteen compounds were synthesized with 3,5-bis?2-carboxylphenoxy?benzoic acid?H3L2?and different ions: [Zn1.5?HL2??bpy?1.5?H2O?]n?14?,{[Zn?HL2??bpe?]·0.5bpe}n?15?,{[Co?HL2??bpy??H2O?2)]·DMF}n?16?,{[Co?HL2??bpe?]·0.5bpe}n?17?,[Ln?L2??DMF??H2O?]n?18-26??Ln = Pr 18,Nd 19,Sm 20,Eu 21,Gd 22,Tb 23,Dy 24,Ho 25,Er 26?and [Eu?L2??DEF??H2O?]n?27??bpy = 4,4'-bipyridine,bpe = 4,4'-vinylenedipyridine?.Compound 14 exhibited a complicated 3-D structure.The carboxylate groups bridge two Zn1 atoms to form a Zn2?CO2?2 unit.Two adjacent units are extended into a 2-D metal-carboxylic layer.Zn2 atoms connected these layers,forming a 3-D structure with a novel arrangement in ABAB mode.Within this framework,Zn atoms are further linked by bpy ligands.Topologically,the whole 3-D structure could be regarded as a?3,4,6?-connected?5.62??64.8.9??56.64.7.82.92?topology.Compounds 15 and 17 are isostructural.The units could be regared as nodes and bpe ligands as linkers.The whole topology can be considered as?4,4?-connected sql net.In Compound 16,topologically,the carboxylate ligands and the cobalt centers could be viewed as 4-connected nodes,forming?4,4?-connected sql topology.Compounds 18-26 are isostructural.The carboxylate ligands linked metal atoms give to a dimeric [Ln2??-CO2?2??-O?2?DMF?2] SBU.These units further connected forming a 3-D framework,?3,6?-connected?4.62?2?42.610.83?topology.1-D channels were formed in these compounds.The phenolic oxygen linked carboxylate groups connect the SBUs generate helical chains.The R-and L-helices are arranged alternately around the channels.Consequently,the whole framework shows no chirality.In compound 27,a similar dimeric [Eu2??-CO2?2??-O?2?DEF?2] SBU is also formed.Each SBU connected with carboxylate ligands,forming a?3,6?-connected?4.62?2?42.610.83?topology.However,the helical of compound 27 was different with above structures.Compound 15 exhibited an emission peak at 392 nm in the solid state at room temperature.It also exhibited pH-dependent fluorescence sensing properties.Compounds 16 and 17 were not only exhibit field-induced single-ion relaxation magnetization but also display great catalytic activities.Compounds 21,23 and 27 can sensitively and selectively detect NB and Cu2+ ions.The quenching constants of NB are 4.74×106,4.74×106 and 1.20×106 M-1,respectively.The detection limits are 64.77,45.35 and 31.88 ppm,respectively.The-?Sm of compound 22 is 16.5 J kg-1-1 at 2 K for ?H of 70 kG.Compound 24 displays significant frequency-dependent out-of-phase signals when a static dc field of 2000 Oe was applied.3.Six compounds were solvothermally synthesized with 1,3,5-tri?2-carboxylphenoxy?benzene?H3L3?and different Ln3+ ions: {[Ln?L3??DMF??H2O?]}n?28-33??Ln = Nd 28,Sm 29,Eu 30,Gd 31,Tb 32,Dy 33?.In these compounds,the metals and carboxylate acid ligands constructed a dimeric Ln2?CO2?4 unit,which were connected through the carboxylate acid ligands to extend into 1-D chains.Compounds 30 and 32 can sensitively and selectively detect NB and Cu2+ ions.The quenching constants of NB are 9.4×105 and 2.0×105 M-1,respectively.The detection limits are 60.36 and 45.11 ppm,respectively.The-?Sm of compound 31 is 21.3 J kg-1 K-1 at 2 K for ?H of 70 kG.Compound 33 also displays significant frequency-dependent out-of-phase signals when a static dc field of 2000 Oe was applied. |
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