Syntheses, Structures, And Properties Of Metal Complexes Containing Substituted Hydrazones Ligands

The substituted hydrazones and their metal complexes have developed rapidly in recent years because of their fascinating structural and potential applications in the fields of enantioselective synthesis, asymmetric catalysis, porous materials, nonlinear optical materials, magnetic materials, probe technique, DNA recognition and so on. Therefore, the rational design, synthesis, and characterization of novel substituted hydrazones and their metal complexes are of fundamental importance for the further developments of supramolecular chemistry and coordination chemistry.In this thesis, a series of new substituted hydrazones and their metal complexes were synthesized. One of the important substituted hydrazones is the acyl-/aroyl-hydrazone compound. These compounds not only display interesting structures, which are assembled by such as coordination bonding, hydrogen bonding, aromaticπ…πstacking and so on, but also exhibit different coordination modes of different aromatic hydrazone ligands. In this paper, we reported the crystal structures, various spectroscopic studies, magnetism, anion or cation recognition, and DNA binding and cleavage activities of the new substituted hydrazone complexes.0.1 Synthesis and characterization of substituted hydrazone compounds.Compared with different synthetic approaches of the compounds, the general solution approach was chosen. The acyl-/aroyl-hydrazone can be seen as the result of the reaction of an aldehyde or a ketone with an acyl-/aroyl-hydrazine that has a free -NH2 group. In suitable experimental conditions using appropriate bridging ligands, we have been successful in synthesizing a series of mono-, di- and polynuclear transition metal complexes with substituted hydrazone ligands. These complexes were characterized by X-ray crystallography, IR, UV-Vis,1H-NMR spectroscopy, and elemental analyses. 0.2 Crystal and molecular structure.As a terminal or bridged-ligand, the hydrazones ligands have the following features:(â…°) Flexibility. It contains N-N and C-C single bonds, which can freely rotate according to the demand of coordination, making the hydrazone ligand as a potential bidentate, tridentate or polydentate chelating ligand. (â…±) The aryl group and acyl-hydrazone (R2C=N-N-CO-R) form a co-planar delocalized molecule. It may construct new structures viaÏ€stacking interactions. It contains aromatic nitrogen heterocycles, in principle, should be well suited forπ…πinteractions because of lowÏ€-electron density resulting from nitrogen heteroatoms, which serve as electron acceptors within the ring.The hydrazone complexes have the following features:(â…°) Novel structures and bonding modes. The structural studies indicate that tridentate acyl-hydrazone ligand has commonly been coordinated to metals at a 1:1 metal/ligand ratio, which allows the formation of molecular polygons, chains or layer and exhibits a rich degree of superstructural diversity. However, the substituted hydrazone ligand also occasionally exhibits as bi-dentated or penta-dentated ligand, for example in complex 3 and 5. (â…±) Non-classical M-Cl…H-D hydrogen bonding. The results indicated that M-Cl moieties were good anisotropic hydrogen-bond acceptors; (â…²) NovelÏ€stacking modes. In this paper we surveyed and analyzed multiple edge-to-face (EF) and offset-face-to-face (OFF) interactions forms in crystal packing. The parallel fourfold aryl embrace (P4AE, comprised of one OFF and two EF) occurs for compounds 20,23,25,27,29; (iv) Trend to form dimers. Among the complexes, the dimers were formed by theπ…π, d…π, M…M, M…Cl, Cl…Cl weak interactions and hydrogen bonding. The complexes contain the asymmetrical N-heterocyclic ligands with a tendency to form chiral complexes (enantiomeric forms), in which the only asymmetric center is the metal itself (chiral-at-metal). The enantiomorph was formed by these weak interactions. 0.3 The theoretical analysis based on calculating results of quantum chemistry.The geometries of the 19,23 were definited by crystal information files. The geometries of the 21 were optimized using the B3LYP/6-31++G** basis set. These geometries were used to perform single point calculations using the Gaussian03 program package. The calculating results show that complexes 23 exist synergistic effects of EF-OFF interactions, and the non-coplanar N atom with aromatic ring possibly participate in delocalizingÏ€system. In the complexes 19,21, the eigenvalue of the dxy orbit has large difference, it is reasonable to conclude that not only the S atom of ligand coordinate to Cu2+, but also the unoccupied d orbit of the S atom can accept the d electron from Cu2+, to form freeback d-dÏ€bonding in complex 21.0.4 Studies on the properties of the compounds.(â…°) Solid-state fluorescence spectral properties. Compared with the solution fluorescence spectra, the most drastic red-shift is observed in the solid-state spectra, which may be assigned to intra-ligand (Ï€â†'Ï€*) fluorescent emission stemming fromπ…πstacking and hydrogen bonding interactions. These interactions play an important role in decreasing the HOMO-LUMO gaps. (â…±) The experimental data of the variable-temperature (2～300 K) magnetic susceptibilities display an antiferromagnetic exchange between the bridged Mn3+ ion in complex 9. (â…²) Interactions of DNA and complexes. Interactions of DNA and the complexes 6-10,12 indicated that complex 7 has higher activity. The UV-Vis titrations of 7 with CT-DNA were done in Tris-HCl buffer medium, and showed significant hypochromism. The gel electrophoresis shows that complex 7 is able to perform an efficient cleavage of pBR322 DNA. When pBR322 DNA was incubated with the 7 in the presence of hydroxyl radical scavengers or reductant-oxidant, inhibition of the DNA cleavage was not observed. These observations suggested that 7-mediated cleavage reaction occurs via a hydrolytic path. (â…³) Studies of the ions recognization. UV-Vis spectral studies show that the host molecule H216 provides strong binding of Zn2+ in a 1:1 ratio in solution. The conditional binding constant of the complex is 1gKZn-16=12.89±0.76 in 0.05 M Tris-HCl buffer at pH 7.4. The change in theΔA353 nm-ΔA311 nm of H216 is more pronounced in the presence of Zn2+ than other metal ions. Therefore, the analysis ofΔA353 nm-ΔA311 nm, with respect to difference spectral changes at 353 and 311 nm, is possible to determine Zn2+. The H216 exhibits an enhanced fluorescence effect by the addition of Zn2+, and affords an excellent selectivity for Zn2+ under physiological conditions. In DMSO/H2O (4:1) system, the adding of F- to the solution of the host molecule H230 caused dramatic changes in color which were clearly visible to the naked eye. However, no significant changes of color were observed when H230 was exposed to Cl-, Br-, I-, OAc-, and H2PO4- respectively. The absorption spectral studies indicated that a good linear relationship between the absorbance and the F- ion concentration could be obtained from 8.5×10-/ to 4.4×10-5 M (R2=0.9946). The detection limit was measured to be 5.8×10-7 M.