Studies Of Novel Coordination Polymers With Diverse Topology Constructed From Bis-(tri-)(imidazole) Or Bis-(pyirdine) Ligands And Their Properties

Metal–organic frameworks （MOFs） are one kind of new and well-designedcoordination functional materials with widely potential applications in diverse areas.Nowadays studies in this field have been focused on three aspects: select suitableorganic ligands to construct the products to obtain the molecular tailor and assemblyby employment of related principle molecular designing and crystal engineering,investigate the structure–property relationships and explore advanced compositematerial with superior properties. Metal-organic frameworks （MOFs） exhibitingentangled architectures are of great interest because of their intriguing aestheticstructures and topological features as well as their promising applications asfunctional materials.In this paper, we selected five different imidazole-containing orpyridine-containing ligands as main ligands, namely, rigid ligands:1,4-bis（1-imidazolyl）benzene （bib）,4,4’-bis（1-imidazolyl）biphenyl （bibp） and1,3,5-tris（1-imidazolyl）benzene （tib） as well as flexible ligands:1,3,5-tris（imidazol-1-ylmethyl）-2,4,6-trimethylbenzene （titmb） and1,3-bis（4-pyridyl）propane （bpp）, and different organic carboxylic acid as co-ligandsto combine with different transitional metal ions (Co^Ⅱ、Zn^Ⅱ、Mn^Ⅱ、Cd^Ⅱ) to obtainnovel entangled systems. All compounds are characterized by elemental analysis, IRspectrum and X-ray crystallography. The crystal structures as well as topologicalanalysis of these compounds and the systematic investigation of the effect of structurecharacteristics of ligands on the ultimate frameworks will be represented anddiscussed. Furthermore, the thermogravimetric analyses, the photoluminescenceproperties, the ferroelectric properties and the magnetic properties of the complexesare discussed in detail. The structure–property relationships were also investigated.Therefore,28novel complexes reported here can be divided into four partsaccording to their N-donor ligands and their characteristics of structures andproperties.（1） A series of metal–organic frameworks （MOFs） based on the rigid bibp ligand （compounds1-12）. Compounds1and2are constructed by metal formate (M=Mn^Ⅱand Co^Ⅱ) and bibp ligands showing1D and3D networks, respectively, due to thedifferent coordination models of formates （chapter2）. Compounds3-8areconstructed by different metal ions (Co^Ⅱ、Zn^Ⅱand Cd^Ⅱ), flexible organic carboxylatesand bibp ligands showing2D （compounds3-5） and3D （compounds6-8） networks,respectively. In particular, compounds3and4are two threefold2D�'3Dpolythreading networks; compound6is a threefold interpenetrating network withunprecedented4-connected （6⁵.8） topology; compound7features rare4-connecteddmp network with fivefold interpenetration; compound8displays a new trinodal（4,8）-connected （3²·4²·5²）（3⁴·4⁸·5⁸·6³·7⁴·8）（3⁴·4⁶·5⁸·6⁸·7²） topological net （chapter2）.Remarkably, compounds9-12are four Co coordination compounds with unusual typeof entanglements which are assembled by the same initial materials by simplychanging the volume ratio of water/DMF medium. Compound9is an unprecedentedentangled structure having both2D�'3D polycatenation and1D+2D�'2Dpolythreading features; compound10is a new trinodal （3,4）-connectedself-penetrating3D network; compound11is a rare threefold2D�'3D polythreadingstructure based on double-layered sheets; compound12displays a2D�'3Dpolycatenated framework formed by five-fold interpenetrated trinodal （3,4）-connectedT-shaped bilayers （chapter3）. In addition, compounds6-8show photoluminescenceproperties. The results of this work indicate that rigid bibp ligand tends to formframework with large voids when coordinating to metal ions because of its length andrigidity, which favors to generate the penetrated networks; it is also a good molecularrod to construct polythreading network when coordinating to metal ions by only oneN atom; solvent preference plays a significant role on the final structure.（2） A series of metal–organic frameworks （MOFs） based on the rigid tib ligand（compounds13-18, chapter4）. Compound13exhibits a2D double-layered sheet with（3,6）-connected kgd topology. Compounds14-18are all3D frameworks. Compound14is obtained by using achiral rigid ligands via spontaneous resolution; the structureis comprised of two crystallographically independent motifs both showing（3,4）-connected self-penetrating nets with the unique （103）2（106）3topology, each ofwhich contains interlaced triple-stranded right-and left-handed Zn–BDC–Zn helical chains, respectively, and two such nets interpenetrate. Compound15is anotherexample showing both self-penetration and interpenetration features with binodal（3,4）-connected （103）2（10⁶）₃topology that is different from compound14.Compounds16and17are both twofold interpenetrating network. Two enantiomericchiral3D （3,4）-connected （10³）₄（10⁶） nets interpenetrate in the former, while twoidentical3D （3,4,5）-connected （4·8²）₂（4²·8⁴）（4³·6²·8⁵）₂（4³·6²·8）₂nets interpenetrate inthe latter. Compound18is a binodal （3,4）-connected3D network with the rare（4·6·8）（4·6²·8·10²） fsx-3,4C2/c-2topology. In addition, compounds13-16showphotoluminescence properties. Compound14also displays ferroelectric behavior. Theresults of this work indicate that rigid tib ligand is a good candidate to be a3-connected nodal and adopts diverse coordination models to afford1D,2D and3Dnetworks when bonding to metal ions. Especially, the twist of imidazole rings andbenzene ring in tib ligand tends to form structures with helical features, which favorsto generate the entangled networks.（3） A series of metal–organic frameworks （MOFs） based on the flexible titmbligand （compounds19-24, chapter5）. Compounds19-24all can be described in termsof M-titmb SBUs pillared by “rod” according to the concept of secondary buildingunit （SBU）, in which M-titmb SBUs exhibit0D molecular cage,2D multi-layeredsheet,1D ladder-like chain and2D sheet due to various coordination models of titmbligand. In particular, compound23features a rare binodal （3,5）-connected （63）（698）hms net with2-fold interpenetration and it displays ferroelectric behavior. In addition,compounds19shows photoluminescence property. The results of this work indicatethat the flexibile titmb ligand possesses various conformations which has significanteffect on the final products and the designed compounds would be obtained byintroduction suitable rigid co-ligands. In addition, the concept of SBU is helpful tounderstand the given crystal structure and to design high-connected networks.（4） A series of entangled metal–organic frameworks （MOFs） based on the rigid bibor flexible bpp ligands （compounds25-28, chapter6）. Compounds25and26wereobtained by the hydrothermal reaction in one pot. Compound25is a2D�'3Dpolycatenation network and compound26is a fivefold2D�'3D polythreadingnetwork. Compound27is a1D�'2D polyrotaxane network with each Co2（L2）2ring threaded by two Co（bib） rods. Compound28is a twofold interpenetrating binodal（4,6）-connected fsh network based on bpp ligand. The results of this work indicatethat the rigid bib ligand is a good candidate for the organization of beautiful MOFsdue to its appropriate length and rigidity. Moreover, flexible bpp ligand is also a goodcandidate for the organization of entangled MOFs.In addition, magnetic studies reveal that compound29demonstrates dominantferromagnetic behavior and compound30displays spin-canting behavior. Bothcompounds29and30exhibit ferroelectric features.