Synthesis, Structures And Application Of N, O Containing Ligands And Their Complexes

The ruthenium complexes of ligands containing 2 or 3 pyridine rings have goodproperties in chemical stability, easy tuning in structure and rich photophysicalbehavior. Their interaction with nucleic acids has been the subject of tremendousresearch interest and has potential to develop spectroscopic probes of DNA structureand cancer therapy agents. Multinuclear manganese complexes of polypyridineligands have played an important role in mimicking the oxygen-evolving center ofphotosystemâ…¡structurally and/or functionally and are applicable in developing watersplitting catalysts. This thesis has described original research work as follows:The reaction between 1,10-phenanthroline-5,6-dione and pyrazole-3-carbaldehydeor imidazole-2-carbaldehyde has generated two new ligands2-(1H-imidazol-2-yl)- 1H-imidazo[4,5-f] [1,10]phenanthroline (IZIP) and2-(1H-pyrazol-3-yl)-1H-imidazo[4,5-f][1,10]phenanthroline (PZIP), respectively.The corresponding ruthemium complexes [(bpy)₂Ru(IZIP)](ClO₄)₂ (denoted as Ru1)and [(bpy)₂Ru(PZIP)](ClO₄)₂ (Ru2) (bpy is 2,2'-bipyridine) have then beensynthesized. Two novel polycyclic compounds rich in N and O atoms have beensynthesized through reactions of 1,10-phenanthroline-5,6-dione withdiethylenetriamine, or reactions of 3,4-dihydroxybenzaldehyde in the presence ofmanganese chloride, respectively. They are (1R)-6,9,15,18,21-pentaazapentacyclo[12.7.0.0^1,18.0^2,7.0^8,13]henicosa-2,4,6,8(13),9,11,14-heptaene and(5R, 10R)-3,8-dihydroxy-5,10-diethoxy-5,10-dihydrochromeno[5,4,3-cde]chromenemonohydrate, respectively. For the latter, two supramolecular isomers have beenobtained. Means of ESI-MS, ¹H NMR, electronic absorption, emission, IRand single crystal X-ray diffraction have been utilized for characterizing and property studies of these compounds.Photophysical methods including electronic absorption, emission and emissionquenching, and viscosity measurement have been used to study the interaction of Ru1,Ru2 with calf thymus DNA. Both complexes bind significantly to DNA, as shown bythe significant differences between the photophysical properties before and afterbinding with DNA. Addition of DNA to Ru1 and Ru2 led to hypochromism in bothultraviolet and visible regions and enhancement of the emission of the two complexes.The emission quenching by K₄[Fe(CN)₆] was decreased greatly when DNA waspresent. The relative viscosity of DNA was raised after adding these two complexes tosaturation with the order Ru1＞Ru2. Since the small planarity of bpy makes it a poormoiety for intercalating DNA, the above facts imply that Ru1 and Ru2 bind to DNAby intercalation of IZIP or PZIP into the DNA base pairs.Three dinuclear manganese complexes [L₂(H₂O)₂Mn₂(μ-O)₂](NO₃)₃, in which Lis 4-tolyl-2,2':6',2"-terpyridine, 4-bromomethylphenyl-2,2':6',2"-terpyridine,4-formylphenyl-2,2':6',2"-terpyridine have been prepared in situ, and their activity ofcatalyzing the oxidation of water to molecular oxygen. The results show that all ofthem can catalyze O₂ evolution reaction with oxidant oxone, but probably because theterminal substituents are far away from and have unconspicuous effect on Mn atoms,the rates of O₂ evolution of the three complexes are close.