Di- and Tetranuclear Ruthenium(II) and/or Osmium(II) Complexes of Polypyridyl Ligands Bridged by a Fully Conjugated Aromatic Spacer: Synthesis, Characterization, and Electrochemical and Photophysical
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- 作者：Anvarhusen K. Bilakhiya ; Beena Tyagi ; Parimal Paul ; and P. Natarajan
- 刊名：Inorganic Chemistry
- 出版年：2002
- 出版时间：July 29, 2002
- 年：2002
- 卷：41
- 期：15
- 页码：3830 - 3842
- 全文大小：175K
- 年卷期：v.41,no.15(July 29, 2002)
- ISSN：1520-510X
文摘
A series of mono-, di-, and tetranuclear homo/heterometallic complexes of Ru(II) and Os(II) based on the bridgingligand dppz(11-11')dppz (where dppz = dipyrido[3,2-a:2',3'-c]phenazine) (BL) have been synthesized andcharacterized. This bridging ligand is a long rigid rod with only one rotational degree of freedom and providescomplete conjugation between the chromophores. The complexes synthesized are of general formula [(bpy)2Ru-BL]2+, [(phen)2/(bpy)2M-BL-M(bpy)2/(phen)2]4+ (M = Ru(II) and Os(II)), [(bpy)2Ru-BL-Os(bpy)2]4+, and [{(bpy)2Ru-BL}3M]8+. Detailed 1H NMR studies of these complexes revealed that each chiral center does not influence itsneighbor because of the long distance between the metal centers and the superimposed resonances of thediastereoisomers, which allowed the unambiguous assignment of the signals, particularly for homonuclear complexes.Concentration-dependent 1H NMR studies show molecular aggregation of the mono- and dinuclear complexes insolution by 
- stacking. Electrospray mass spectrometry data are consistent with dimerization of mono- anddinuclear complexes in solution. Electrochemical studies show oxidations of Ru(II) and Os(II) in the potential ranges+1.38 to +1.40 and +0.92 to +1.01 V, respectively. The bridging ligand exhibits two one-electron reductions, andit appears that the added electrons are localized on the phenazene moieties of the spacer. All of these complexesshow strong metal-to-ligand charge-transfer (MLCT) absorption and 3MLCT luminescence at room temperature.Quantum yields have been calculated, and the emission lifetimes of all complexes have been measured by laserflash photolysis experiments. The luminescence intensity and lifetime data suggest that the emission due to the Rucenter of the heteronuclear complexes is strongly quenched (>90%) compared to that of the corresponding modelcomplexes. This quenching is attributed to intramolecular energy transfer from the Ru(II) center to the Os(II) center(k = (3-5) × 107 s-1) across the bridging ligand.
- stacking. Electrospray mass spectrometry data are consistent with dimerization of mono- anddinuclear complexes in solution. Electrochemical studies show oxidations of Ru(II) and Os(II) in the potential ranges+1.38 to +1.40 and +0.92 to +1.01 V, respectively. The bridging ligand exhibits two one-electron reductions, andit appears that the added electrons are localized on the phenazene moieties of the spacer. All of these complexesshow strong metal-to-ligand charge-transfer (MLCT) absorption and 3MLCT luminescence at room temperature.Quantum yields have been calculated, and the emission lifetimes of all complexes have been measured by laserflash photolysis experiments. The luminescence intensity and lifetime data suggest that the emission due to the Rucenter of the heteronuclear complexes is strongly quenched (>90%) compared to that of the corresponding modelcomplexes. This quenching is attributed to intramolecular energy transfer from the Ru(II) center to the Os(II) center(k = (3-5) × 107 s-1) across the bridging ligand.