| Ionic liquids(ILs)have been referred to as "designer solvents" because of their physical properties,including melting point,density,viscosity,and miscibility with water,which can be easily altered by judicious choice of cations and anions.Ionothermal synthesis,which uses of ionic liquids as solvent,structure directing agent or charge compensating species in synthesis of crystalline solids,offers many advantages over conventional hydrothermal and solvothermal synthesis methods.The ionothermal method has opened up a new route for the creation of novel materials.In this thesis,18 novel organic-inorgnaic hybrid compounds or coordination polymers have been successfully synthesized under ionothermal conditions by utilization of a series of imidazolium ion liquids as solvent.All the compounds have been characterized by single crystal X-ray diffractions,X-ray powder diffractions,elemental analysis,infrared spectra,diffuse reflectance spectra,photoluminescence,thermogravimetric analyses,cyclic voltammetry,ferroelectric property and photocatalytic activity.The detailed progresses are as following:By controlling the molar ratios of reaction sources,the temperature and reaction time,the self-assemblies of a-Keggin anions,[XW2O40]3-(X = P,Si)and 1-alkyl-3-methylimidazolium ion liquids under ionothermal conditions lead to six inorganic-organic hybrid compounds 1-6.All these hybrid solids can be described as three-dimensional supramolecular frameworks generated by C-H…O weak hydrogen bonds.Furthermore,we also discuss the influences of the ionic liquid cations on the formation of these hybrid supramolecular compounds.Complexes 1-6 are shown good photocatalytic activity.The ionothermal reactions of Zn,Cd or In salts with aromatic carboxylic ligands(1,2,4,5-benzenetetracarboxylic acid,1,3,5-benzenetricarboxylic acid,3,5-di(4'-carboxyl-phenyl)benozoic acid,isonicotinic acid,and 3,5-dicarboxy l-(3 ',5 '-dicarboxylazopheny)benzene)have given birth to 12 novel coodiantion polymers varying from one-to three-dimensions.In the synthesis of compounds 7-9,the ion liquids only act as the reaction solvents.For the two-dimensional coordination polymer 10,the cation and anion of ion liquid solvent both exist in the ultimate framework.The Br-or I-anions help to saturate the coordination sphere of In3+ in complexes 11 and 12 to generate two one-dimensional chains with iso-structures.The ionothermal reaction of In3+ and 1,2,4,5-BTC ligands in[EMI]Br gave rise to crystals of 13 and 14,which both show three-dimensional porous frameworks.One-dimensional channels along the c-axis direction exist in these two compounds,which also shown similar rod-packing topologies.Compounds 15-18 have isomeric[Zn3(1,2,4,5-BTC)2]n2n-three-dimensinal anionic frameworks,which are introduced by the imidazolium cations from ion liquid solvent.The successful preparation of these four supramolecular isomers mainly ascribed to the novel ionothermal method.Copmpound 15 is the first ionothermal case of a 3D ferroelectric metal-organic framework with colossal dielectric constant.The saturation spontaneous polarization(Ps),remanent polarization(Pr),and coercive field(Ec)are about 48.73 nC cm-2,17.93 nC cm-2,and 0.21 kV cm-1,respectively.The asymmetric structure of the[EMI]+ cations is a key factor to the formation of helical chains in 15,which further lead to the non-centrosymmetric packing arrangement.In conclusion,the ionothermal synthesis is a novel methodology for the development of crystal engineering.and it can be expected that in the near future there will be further publications reporting new and exciting structures and developments.We believes what we presented in this thesis will be helpful for the further development of ionothermal sysnthesis. |
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