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 Studies

Abstract

A series of mono-, di-, and tetranuclear homo/heterometallic complexes of Ru(II) and Os(II) based on the bridging ligand dppz(11-11')dppz (where dppz = dipyrido[3,2-a:2',3'-c]phenazine) (BL) have been synthesized and characterized. This bridging ligand is a long rigid rod with only one rotational degree of freedom and provides complete conjugation between the chromophores. The complexes synthesized are of general formula [(bpy)(2)Ru-BL](2+), [(phen)(2)/(bpy)(2)M-BL-M(bpy)(2)/(phen)(2)](4+) (M = Ru(II) and Os(II)), [(bpy)(2)Ru-BL-Os(bpy)(2)](4+), and [((bpy)(2)Ru-BL)(3)M](8+). Detailed (1)H NMR studies of these complexes revealed that each chiral center does not influence its neighbor because of the long distance between the metal centers and the superimposed resonances of the diastereoisomers, which allowed the unambiguous assignment of the signals, particularly for homonuclear complexes. Concentration-dependent (1)H NMR studies show molecular aggregation of the mono- and dinuclear complexes in solution by pi-pi stacking. Electrospray mass spectrometry data are consistent with dimerization of mono- and dinuclear 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, and it appears that the added electrons are localized on the phenazene moieties of the spacer. All of these complexes show strong metal-to-ligand charge-transfer (MLCT) absorption and (3)MLCT luminescence at room temperature. Quantum yields have been calculated, and the emission lifetimes of all complexes have been measured by laser flash photolysis experiments. The luminescence intensity and lifetime data suggest that the emission due to the Ru center of the heteronuclear complexes is strongly quenched (>90%) compared to that of the corresponding model complexes. This quenching is attributed to intramolecular energy transfer from the Ru(II) center to the Os(II) center (k = (3-5) x 10(7) s(-1)) across the bridging ligand.

Synthesis, DNA Cleavage Activity, Cytotoxicity, Acetylcholinesterase Inhibition, and Acute Murine Toxicity of Redox‐Active Ruthenium(II) Polypyridyl Complexes

“…Anal. calcd for C 70 H 46 F 24 [(Ph 2 phen) 2 Ru(tatpp)Ru(Ph 2 phen) 2 ][PF 6 ] 4 ,[ 4 Ph ][PF 6 ] 4 :Amixture of tatpp (0.1 g, 0.21 mmol) and Ru(Ph 2 phen) 2 Cl 2 (0.42 g, 0.5 mmol) was suspended in 15 mL of ethanol and 15 mL of water and held at reflux for 7d ays under N 2 .T he mixture was then stored at 4 8C for 12 ha nd filtered. The addition of aqueous NH 4 PF 6 resulted in ap recipitate, which was isolated by filtration and washed with 10 mL of water (3 )a nd 10 mL of ethanol (3 ).…”

“…Such aggregations appear to be common in RPCs with large planara romatic ligands [21a, 22] and have been reportedf or [(phen) 2 Ru(tpphz)] 2 + (5 2 + ) [23] as well as an umber of related complexes. [24] Ad iscussion on the effecto fa ggregationa nd Zn 2 + complexation as am eanso fb reaking up this aggregation is given in the Supporting Information. Notwithstanding this complication, the 1 HNMR for all monomeric Ru-tatpp complexes are consistent with the proposed structures.…”

Detection of NaCN in aqueous media using a calixarene-based fluoroionophore containing ruthenium(ii)-bipyridine as the fluorogenic unit

“…† It should be noted that the CV of the complex 1 exhibited a quasireversible redox wave at the potential 1.35 V and the DPV also showed an oxidation wave at the same potential, which is attributed to Ru(II) / Ru(III) oxidation. 36,44,45 The CV and DPV of 1 were again recorded under similar experimental conditions in the presence of excess amounts (50 molar equivalent) of TBA salts of CN À and AcO À . The DPV of 1 before and aer addition of CN À and AcO À are shown in Fig.…”

Synthesis, photophysical, and electrochemical properties of two polynuclear ruthenium(II) polypyridyl complexes containing diazafluorene

“…p* transitions. Assignments of the absorption bands of the complexes were made on the basis of the well-documented optical transitions of analogous Ru(II) polypyridyl complexes [23][24][25][26]. The absorption spectra of the complexes both show three well-resolved bands.…”