Synthesis,Structure And Characterization Of Polypridyl And Their Complexes

There are extensive interests in synthesis and properties of 2,2'-bipyridyl derivative with specifical function. Due to their coordinate ability to the metal, they have become one of most popular chelated ligands. Since ligand structure has important effect on electrochemical and photochemical properties of the complexes, many research works focused on substituting groups in aromatic ring. In this paper, a series of 4,4'-substitued-2,2'-bipyridyl and their Ru(II) complexes with electron-donating and electron-withdrawing substituents are synthesized and characterized with 2,2'-bipyridyl as raw material. The properties of ligands and their Ru(II) complexes are investigated in detail. Three crystal structures have been discussed.A series of 4,4'-substitued-2,2'-bipyridyl was synthesized by using 2,2'-bipyridyl as the starting material with a successive processes, such as N-oxidation, nitrification, halogenation, deoxygenation and silicification reaction. These ligands, 4,4'-dibromo-2,2'-bipyridyl, 4,4'- dimethoxy-2,2'-bipyridyl, 4,4'-bis(trimethylsilyl)-2,2'-bipyridyl and 4,4'-dinitro-2,2'-bipyridyl, are obtained. They are characterized with IR, 1H-NMR and element analysis. In the solution of methylene chloride, the result of UV-Vis absorption and emission reveals that electranical structure of ligang play an important role to their optical activities. The ligand with trimethylsilyl shows the strongest emission intensity, the poorest to that with nitro.The Ru(II) complexes have been alslo synthesized through the reaction between a series of 4,4'-substitued-2,2'-bipyridyl and cis-Ru(bpy)₂·Cl2·2H₂O. They are characterized with IR, element analysis, 1H-NMR, UV-Vis, emission spectra and X-ray diffraction. The UV-Vis spectra of Ru(II) complexes were collected in acetonitrile. The complexes with nitro and bromine atoms show the strongest and the poorest absorption respectively, while the MLCT bands at about 450 nm. Excitated at 450 nm, Ru(II) complexes sent emission at about 610 nm. The trimethylsilyl -substituented complex shows the strongest emission intensity, the weekest emission intensity for the nitro-substituented complex. The investigation of electrochemical behavior showed that these four Ru(II) complexes are irreversible in acetonitrile with LiCl·H₂O as the supporting electrolyte. We have also acheived single crystal materials of [Ru(bpy)₂(4,4′-dibromo-2,2′- bpy)]²⁺·2(PF6-) and [Ru(bpy)₂(4,4-dimethoxy-2,2′-bpy)]²⁺·2(PF6-). Some information of structure is shown in detail.