The Molecular Architecture And Studies Of Functional Coordination Polymers Based On V-shaped 2,5-bis(4-pyridyl)-1,3,4-thiadiazole

The design and construction of coordination polymers with intriguing structural motifs, unique chemical and physical properties leading to potential applications in catalysis, luminescence, magnetism, sorption, ion exchange, nonlinear optics and electricity has been attracting enormous interest in coordination chemistry and material chemistry. In the realm of the controllable construction of the title polymers, the crystal engineering of coordination frameworks is an effective method. In this regard, much attention has been devoted to the deliberate control of self-assembly infinite coordination networks via selecting different ligands, metal ions, solvent system, synthetic methods and so on. Especially, rational design and considerate selecting special organic structure through appropriative approach of assembly should be the key in constructing target polymers, which is a great challenge for chemical researchers. In this dissertation, aiming at synthesizing novel materials with esthetics and excellent properties, the V-shaped neutral 2,5-bis(4-pyridyl)-1,3,4-thiadiazole and multi-functional polycarboxylate as building blocks under the intervention of various transition metal ions have been selected to construct 23 coordination polymers by assembly principle of crystal engineering. They are listed as follows: [Co(bpt)(pm)_0.5(H₂O)]_n·3nH₂O (1), [Cu₂(bpt)(pm)(H₂O)₄]_n (2), [Co(bpt)(pydc)]_n·2nCHCl₃·nH₂O (3), [Cu₂(bpt)(pydc)₂(H₂O)₂]_n (4), [Cu₂(bpt)(pydco)₂(H₂O)₂]_n·nH₂O (5), [Cd(bpt)(pydco)]_n (6), [Mn(bpt)(oba)(H₂O)₃]_n·nH₂O (7), [Co₂(bpt)₂(oba)(H₂O)₇]·(oba) (8), [Cd₂(oba)₂(H₂O)₆]_n·2n(bpt)·2nH₂O (9), [Cu₄(bpt)₄(oba)₄ (H₂O)₂]_n·7nH₂O (10), [Cu₂(bpt)(ox)₂]_n·2.92nH₂O (11), [Cu(bpt)(mal)(H₂O)]_n·2nH₂O (12), [Cu(bpt)(glu)]_n (13), [Cu(bpt)(adi)]_n (14), [Cu(bpt)(fum)]_n·2nH₂O (15), [Cd₂(bpt)(ox)₂]_n·X (16), [Cd(bpt)(mal)(H₂O)]_n (17), [Cd(bpt)(suc)]_n (18), [Cd(bpt)(glu)]_n·nH₂O (19) [Cd₂(bpt)₂(male)₂]_n·2nH₂O (20), [Cd(bpt)(fum)(H₂O)]_n·nH₂O (21) and [Cu₄(bpt)₄(oba)₄]_n (L-22 and D-22). The target coordination polymers have been characterized by elemental analyses, IR spectra, fluorescence spectroscopy, thermal analysis, XRPD analysis and X-ray single crystal diffraction. The systematic investigation of the role of metal ions, organic ligands and different synthesis methods has also be represented and discussed. The results revealed that the introduction of the O-containing rigid aromatic polycarboxylate auxiliary ligands may affect the self-assembly of polymers and lead to new structural evolution. Complex 1 exhibits a 3-D 4-connected structure with 1-D nanosized open channels encapsulated lots of water molecules. Complex 2 represents a 2-D grid. Complexes 3 and 6 were obtained with highly undulated 2-D layers. The interlayers of 3 are filled with two kinds of solvent molecules, whereas 6 is a double-layered framework. Complexes 4 and 5 consist of two distinct 1-D infinite chains held together to form different 2-D supramolecular networks. When the flexible 4,4'-oxybis(benzoic acid) is introduced into the synthetic system, various structural motifs based on different metal ions have been obtained. Complex 7 is a side-armed one dimensional chain, in which two types of helical H-bonded chains appear simultaneously. Complex 8 is composed of cationic binuclear units and oba counterions. Complex 9 contains 1-D zigzag chains. Complex 10 consists of the puckered (4,4) 2D Cu-oba layers with the bpt lateral arms. Non-covalent hydrogen bonding interactions extend complexes 7-10 into high dimensional supramolecular architectures. Interestingly, complex 10 represents a fascinating type of 2D→3D polythreaded architecture with different side arms involving nine polymeric units at a time, which exhibits the highest threaded degree presently known for 2D motifs. Furthermore, the introduction of different aliphatic polycarboxylates leads to distinct coordination polymers. Complex 11 and 16 are 3D porous frameworks which the open channels of the former possess infinite 1D water chains. Complexes 12,13,17 and 19-21 are 2D layers. In particular, the H-bonded units support the coordinate layers of complex 12 into a 2-fold interpenetrated supramolecular net; complex 19 is the 2D bilayer structure with the meso units. Both complexes 14 and 15 are 3Dα-Po 2-fold interpenetrating networks. Differently, discrete tetrameric water clusters exist in the micropores of the MOF 15. Complex 18 is the meso compound, which the bpt pillars extend the layers of two kinds of chiral helices into a pillared-grid MOF. It can be concluded that the conformation and crystal structure of the polymers may depend on the spacer length and flexibility of the aliphatic dicarboxylate chains. More interestingly, spontaneous resolution took place in the course of crystallization of copper-based coordination polymer: compounds L-22 and D-22 represent the first arm-shaped 3-fold interpenetrating enantiomerically chiral MOFs constructed from achiral symmetrical mixed-ligands. As we know, the spontaneous resolution from achiral starting materials occasionally occurred, and the interpenetrating chiral 3D frameworks constructed from symmetrical ligands without any chiral auxiliary are more unusual. Additionally, fluorescent properties of Cd-based complexes have also been investigated, and the results indicate that they could be used as the potential optics materials.