Syntheses And Properties Of Diruthenium Complexes And Their Assemblies

Polynuclear metal complexes are promising candidates for functional materials owing to their rich luminescent,electronic,magnetic properties.Considerable effort has been devoted to the design and preparation of polynuclear metal complexes with novel structures and desired properties.More dirutheumn complexes with interesting properties such as redox activity,luminescence and catalysis will be prepared because of their abundant electron transfer capability.Oxo-bridged dirutheumn complexes are redox-active species and good molecular components for assembling multi-nuclear complexes.The main research work of this paper is as follows:1.Diruthenium complex[Ru2(?-O)(?-OOCCH3)2(2,2'-bpy)2(H20)2](PF6)2(1)(2,2'-bpy=2,2'-bipyridine)was synthesized and used as a precursor for the preparation of series of new compounds Complex[Ru2(?-OX)(?-OOCCH3)2(2,2'-bpy)2(CH3CN)2](PF6)2(2)was prepared by simply dissolving(1)in an acetonitrile solution where the coordinated water molecules were replaced by acetonitrile.Complex(2)showed two redox processes for the diruthenium centers.2.Complex[Ru2(?O)(?-OOCCH3)2(2,2'-bpy)2(H2O)2](ClO4)2(3)was obtained by exchanging the anion ions of(1)in the aqueous solution.The X-ray crystal structure analysis revealed that the bond length and the bond angles of the diruthennium core were somewhat different from those in(1),suggesting that some influence from the anion and the intermolecular interactions.The electronic absorption spectra and the redox potentials of complex(3)in aqueous solutions with various pH values have been investigated.The redox properties of complex(3)in aqueous solutions are pH dependent due to the protonation at the oxo bridge and the deprotonation of the aqua ligands.3.Four new complexes were synthesized by substituting the ligand L of[Ru2(?-O)(?-OOCCH3)2(2,2'-bpy)2L2](PF6)2(L=H2o,CH3CN)with SCn-,OCN-,N3-and 4,4'-bpy,separately.The complexes were characterized by 1H NMR,MS,IR and UV-visible spectroscopy.The crystal structure of the thiocyano compound was determined by X-ray diffraction analysis.The thiocyannide ligand is N-coordinated to the ruthenium centers.Thermal gravimetric analysis showed that the thermal stability of four complexes were better than complexes(1)and(2).Complex[Ru2(?-O)(?-OOCCH3)2(2,2'-bpy)2-(4,4'-bpy)2](PF6)2(4,4'-bpy=4,4'-bipyridine)(7)showed a multi-step redox behavior.4.Complexes[Fe(CN)5(NO)]2-and[M(CN)6]3-(M?Co(?),Fe(?))were used to react with complex(1)to prepare heteronuclear Ru-Co and Ru-Fe complexes.Two cyano-bridged complexes were obtained by reacting[M(CN)6]3-with complex(1),whereas a nitroso-bridged complex was obtained by reacting[Fe(CN)4(NO)]2-and complex(1).The heteronuclear complexes were characterized by IR and UV-visible spectroscopy.Thermal gravimetric analysis showed that the terminal cyanide ligands had decomposed before 130?,when the cyanide bridge and the nitroso bridge began to decompose after 220?,suggesting the cyanide bridge and the nitroso bridge had a better thermal stability compared with the terminal cyanide ligands.