Synthesis And Structures Of Copper Coordination Complexes Based On Pyridyl Schiff-base Ligands

The rational design and research of coordination architectures possessing novel structuresand special functions represent one of the rapidly developing fields in current coordination andsupramolecular chemistry. This thesis focuses on the design and syntheses of Cu(â… )/Cu(â…¡)pyridyl based Schiff-base coordination complexes. Three isomeric multi-topic Schiff-baseligands containing N and O coordination atoms with different terminal pyridine groups, andeleven other copper complexes were synthesized and their structures were studied. The workprovides some new methods and thoughts in the controlled design of functional coordinationcompounds.The thesis is divided into three chapters.In the first chapter, the concept, history and application of coordination chemistry andSchiff-base complexes are concisely introduced. The background of this work is also brieflyreviewed with the emphasis on the current survey of supramolecular isomerism/polymorphismand the metalloligands strategy for constructing coordination polymers. In addition, thesignificancy of this work was also described.In the second chapter, the reactions of ligand 4-pyridylcarbaldehyde isonicotinoylhydrazone (L3) with Cu₂O under solvothermal conditions have been carried out. During theprogress three concomitant polymorphs [Cu(L3)₂] 1 and 2, [Cu(L3)₂]_n 3 were found in the sameTeflon-lined reactor. Their crystal structures were determined by single-crystal X-ray diffractionand the differences between their thermodynamic properties were studied throughthermogravimetric analyses. On the other hand, two 1D mixed-valence Cu^â… Cu^â…¡pseudo-polymorphs: [Cu₂(L1)₂I? H₂O] 4 and [Cu₂(L1)₂I? DMF] 5 were prepared by layeringmethod with the reaction of 2-pyridylcarbaldehyde isonicotinoyl hydrazone (L1) and CuI usingdifferent solvents. The effects of solvent molecules on the structures of complexes have beendiscussed. It is found that the guest solvent molecules serve as highly selective templates duringthe assembly of these host frameworks through steric effects.The third chapter focuses on the systematic investigation of the influences ofpyridine-based Schiff-base ligand geometries on the construction of metalloligand and coordination polymer architectures. In an attempt to analyze how the architecture of coordinationpolymer was affected by the position of N_pridyl donor atom, we have prepared three isomericmulti-topic Schiff-base ligands: 2-pyridylcarbaldehyde isonicotinoyl hydrazone (L1),3-pyridylcarbaldehyde isonicotinoyl hydrazone (L2) and 4-pyridylcarbaldehyde isonicotinoylhydrazone (L3). The reactions of L1-L3 as ligand and Cu₂O with the molar ratio of 1:2 undersolvothermal conditions have been carried out, and three complexes: [Cu(L1)₂] 6, [Cu(L2)₂]_n 7and [Cu(L3)₂] 8, were obtained. Single-crystal X-ray diffraction reveals that 6 and 8 aremonomer with "free" donor groups for further metal binding, however 7 adopts a 1D helix chainstructure. Based on the self-assembly of CuCN and the ligands L1-L3, three novel coordinationpolymers: [Cu₄(CN)₃(L1)₂]_n 9, [Cu₂(CN)₂(L2)]_n 10 and {[Cu₂(CN)_1.5(L3)]? .25H₂O}_n 11, weresynthesized and characterized under solvothermal conditions. In the peculiar architecture of 9and 11, the formation of metalloligand [Cu(L1)₂] and [Cu(L3)₂] acted as 2-cormected and4-connected node play an important role. However, in 10 the metalloligand [Cu(L2)₂] does notform, which may due to the asymmetry of [Cu(L2)₂]. The resulting complexes indicate that theinfluence of the position of N_pridyl donor atom on the networks is significant.