Syntheses,Structures And Properties Of Coordination Polymers Based On Linear Pyridine Ligands

This paper includes four parts.Firstly,we synthesize a 2D coordination polymer containing free ligand L1 based on a rigid linear ligand under the ambient conditions.Through the combined stimuli of temperature and solvent,we study the mutation phenomenon of free ligand L1 in single-crystal structural transformation process.Secondly,three different coordination polymers have been co-crystallized in a one-pot reaction based on a flexible tricarboxylic acid ligand and a rigid pyridine ligand.Combining with the DFT calculation results,through optimizing the conditions of crystallization,three kinds of single component crystals have been obtained.Thirdly,we synthesize four coordination polymers with a rigid linear pyridine and a flexible dicarboxylate ligand based on different metal ions.At the same time,we study the fluorescence and adsorption properties.Four,five new coordination polymers have been synthesized based on pyridine-containing ligands and different carboxylate ligands,as well as transition metal ions.Their structures and spectroscopy properties were discussed in deeply.1.The Mutation Phenomenon in Single-Crystal to Single-Crystal Structural Transformation Process Induced by the Combined StimuliUnder the ambient conditions of 4,4'-(2,5-dimethoxy-1,4-phenylene)dipyridine(L1)and 1,3,5-benzenetricarboxylic acid(H3BTC)in the presence of cobalt salt yielded a 2D coordination polymer containing a free L1 ligand:{[Co(L1)(HBTC)]·0.5(L1)}n(1).Considering the feature of guest molecule for the free L1 ligand and its distance with metal center,we have first make a heating treatment for the crystal sample(named thermal stimulus)to observe the behavior of L1 in the structure.Variable temperature single crystal X-ray diffraction shows that this single stimulus of heating up can not change the location of L1 ligand.Then we select low boiling point solvents for soaking treatment at room temperature about two weeks(named solvent stimulus):CH3OH,CH3CN,(CH3)2CO,CH2Cl2,DMF,H2O,CH3OH/H2O,CH3CN/H2O,(CH3)2CO/H2O,CH2Cl2/H2O,DMF/H2O and CH3OH/DMF.Infrared spectroscopy and PXRD detection results show that this single stimulus of solvent soaking also can not change the location of L1 ligand.Therefore,we select temperature and solvent to make a combining stimuli to monitor the change of L1 molecule in the crystal lattice.When DMF/H2O were used as the solvent system,starting from 50? with the interval of 10?,the distance of hydrogen bond construced from L1 ligand and uncoordinated carboxyl is slowly reduced.Meanwhile,the L1 ligand is slowly attracted to the center of cobalt ions before 95?.When at 95?,L1 is suddenly combined to cobalt ion to form a intricate 3D structure:{[Co5(L1)5(HBTC)2(BTC)2]·6H2O}n(8-11).This occurs in the process of single-crystal to single-crystal transformation and the causes were confirmed by DFT calculation.2.Three Different Metal-organic Frameworks Derived From One-pot Crystallization and Their Controllable SynthesisThree different Co-MOFs,[Co3(L)2(DPDP)]n(12),[Co(HL)(DPDP)]n(13)and{[Co(HL)(0.5DPDP)3(H2O)]·H2O}n(14)(H3L?4,4',4"-(nitrilotris(methylene))tribenzoic acid,DPDP=4,4'-(2,5-dibutoxy-1,4-phenylene)dipyridine))have been co-crystallized in a one-pot reaction.Complex 12 consists of a centrosymmetric trimetallic unit,complex 13 consists of a entrosymmetric dinuclear cobalt center,and complex 14 is a mononuclear structure.Complex 12 is a new topology with the point symbol of {42·6}2{44·610·79·85}.Complex 13 is 2D network,which can be simplified to an sql net with point symbol {44·62}.The network of complex 14 is topologically classified as a uninodal 2-fold interpenetrating net with the bnn[hexagonal boron nitride]topology.We focused on their magnetic behavior.The results of magnetic fitting show that the high-spin Co? ions in 12-14.There is weak ferromagnetic intra-complex magnetic interaction in complex 12 and weak antiferromagnetic interaction between Co? ions in complex 13.The high-spin Co? ions can be confirmed by the spin density distributions on three different cobalt centers.DFT calculation results shown that both the ground state energies and the gaps of frontier molecular orbital energy are close for 12 and 13,but different from 14.Combining with the appearance and proportion of the initial crystallization products,to optimize the conditions of crystallization,mainly through the solvent type and proportion,we have obtained three kinds of one-component crystals,finally.3.Syntheses and Properties of Coordination Polymers Based on Different Metal IonsFour coordination polymers with different metal ions have been synthesized based on a rigid linear pyridine ligand and a flexible V-shaped dicarboxylate ligand(L1=4,4'-(2,5-dimethoxy-1,4-phenylene)dipyridine;H2OBA=4,4'-oxydibenzoic acid):{[Co(L1)(OBA)]·2H2O}n(15),[Zn(L1)(OBA)·2H2O]n(16),{[Ni(L1)(OBA)]·DMF·H2O}n(17),[Cd(L1)(OBA)]·DMF·H2O}n(18).The reaction conditions are similar except metal ions for complexes 15-18.Complexes 15 and 16 present a 3D hxg-d-4-Cccm net,but 17 and 18 are 4-connected sql nets with point symbol {44·62}.These complexes have been characterized by single crystal X-ray diffraction,infrared spectroscopy,thermogravimetry,elemental analysis,and powder X-ray diffraction measurements.UV-visible spectra,fluorescence and gas adsorption properties of the compounds have also been explored.4.Structures and Properties of Coordination Polymers Based on Pyridine Ligands with Flexible Branched ChainsTwo rigid linear ligands with alkoxy functional groups(L1?4,4'-(2,5-dimethoxy-1,4-phenylene)dipyridine;L2=4,4'-(2,5-diethoxy-1,4-phenylene)dipyridine)incorporating carboxyl-containing auxiliary ligands(isophthalic acid=H2IPA;terephthalic acid=H2TPA;biphenyl-4,4'-dicarboxylate?H2BPDC)have been adopted to build a series of complexes with M(?)(M=Zn,Co,Cd)under solvothermal conditions.The formula of these complexes are {[Zn(L1)(IPA)]}n(19),{[Zn(L1)(TPA)]-DMF}n(20),{[Co(L1)(TPA)(H2O)2]-2DMF}n(21),{[Cd(L1)(TPA)(H2O)2]·2DMF}n(22),{[Co(L2)(BPDC)]·0.5H2O}n(23).Five complexes have been characterized by elemental analysis,infrared spectroscopy,powder X-ray diffraction and thermogravimetry measurements.Topological analyses reveal that complex 20 is a 6-connected pcu net with point symbol {412.63},while complex 23 is a 6-connected rob net with point symbol {48.68.8},the other complexes 19,21,22 can be simplified as 4-connected sql nets with point symbol{44.62}.Complexes 19,21,22 are 2D layer motifs,20 and 23 are both two-fold interpenetrating 3D frameworks.The optical absorption spectra of 20 and 23 indicate that they own the nature of semiconductivity.The strong fluorescence emissions and long emission lifetimes of 19,21 and 22 display that they are promising phosphorescent materials.