Competitive energy and electron-transfer quenching across the peptide-bridge in polypyridine ruthenium(II)/osmium(II) binuclear systems

Furue, Masaoki; Ishibashi, M; Satoh, Akiko; Oguni, Tadayoshi; Maruyama, Kei; Sumi, Katsuhiro; Kamachi, Mikiharu

doi:10.1016/s0010-8545(00)00244-7

Cited by 18 publications

(6 citation statements)

References 16 publications

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“…Emission quenching can result from excited-state electron transfer, energy transfer, or a combination of both processes. – Quenching of [Ru(bpy) 3 ] 2+ * emission in the presence of Cu 2+ can occur by excited-state electron transfer from [Ru III (bpy) 2 (bpy •- )] 2+ * to form a charge-separated state Ru 3+ and Cu 1+ , ,, but this can be experimentally challenging to confirm. Conversely, the spectral overlap of the [Ru(bpy) 3 ] 2+ emission band with the (weak but) broad absorbance band of [Cu(bpy) 2 ] 2+ can result in energy transfer quenching.…”

Section: Resultsmentioning

confidence: 99%

Aminoethylglycine-Functionalized Ru(bpy)₃²⁺ with Pendant Bipyridines Self-Assemble Multimetallic Complexes by Copper and Zinc Coordination

2008

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Directed self-assembly using inorganic coordination chemistry is an attractive approach for making functional supramolecular structures. In this article, the synthesis and characterization of Ru(bpy) 3 (2+) compounds derivatized with aminoethylglycine (aeg) substituents containing pendant bipyridine (bpy) ligands is presented. The free bpy ligands in these complexes are available for metal chelation to form coordinative cross-links; addition of Cu (2+) or Zn (2+) assembles heterometallic structures containing two or three transition-metal complexes. Control over relative placement of metal complexes is accomplished using two strategies: two bipyridine-containing aeg strands tethered to Ru(bpy) 3 (2+) allow intramolecular coordination and result in a dimetallic hairpin motif. Ru(bpy) 3 (2+) modified with a single strand forms intermolecular cross-links forming the trimetallic complex. Each of these is characterized by a range of methods, and their photophysical properties are compared. These data, and comparison to an acetyl aeg- modified Ru(bpy) 3 (2+) complex, confirm that the metal ions cross-link bpy-containing aeg strands. Heterometallic complexes containing bound Cu (2+) cause a dramatic reduction in the Ru(bpy) 3 (2+) quantum yields and lifetimes. In contrast, the Ru(bpy) 3 (2+) hairpin with coordinated Zn (2+) has only a slight decrease in quantum yield but no change in lifetime, which could be a result of steric impacts on structure in the dimetallic species. Analogous effects are not observed in the trimetallic Ru-Zn-Ru structures in which this constraint is absent. Each of these heterometallic structures represents a facile and reconfigurable means to construct multimetallic structures by metal-coordination-based self-assembly of modular artificial peptide units.

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Section: Resultsmentioning

confidence: 99%

Aminoethylglycine-Functionalized Ru(bpy)₃²⁺ with Pendant Bipyridines Self-Assemble Multimetallic Complexes by Copper and Zinc Coordination

2008

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“…6 There exist a number of means to fine-tune these features via made-to-order modifications on peripheral ligands. 7 Rhenium polypyridine complexes are known to act as photocatalysts and electrocatalysts for reducing CO 2 to CO. 8 A major problem with these photocatalysts is the lack of an extended absorption into the visible region. The present approach is to fabricate supramolecules of the rhenium complex linked covalently to the ruthenium complex as a visible-light absorber.…”

Section: Introductionmentioning

confidence: 99%

“…Many multinuclear compounds containing two or more metallic sites have been synthesized, and their optical, electronic, and photophysical properties have been studied. , In particular, ruthenium and rhenium polypyridine complexes are popular in both fundamental studies and applications. , These complexes form appealing subunits for nanoscaled devices because of their strong visible absorption, their advanced photochemical and redox properties, and their stability against photodecomposition . There exist a number of means to fine-tune these features via made-to-order modifications on peripheral ligands . Rhenium polypyridine complexes are known to act as photocatalysts and electrocatalysts for reducing CO 2 to CO .…”

Section: Introductionmentioning

confidence: 99%

Architecture of Supramolecular Metal Complexes for Photocatalytic CO₂ Reduction: Ruthenium−Rhenium Bi- and Tetranuclear Complexes

et al. 2005

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We study the electrochemical, spectroscopic, and photocatalytic properties of a series of Ru(II)−Re(I) binuclear complexes linked by bridging ligands 1,3-bis(4′-methyl-[2,2′]bipyridinyl-4-yl)propan-2-ol (bpyC 3 bpy) and 4-methyl-4′-[1,10]phenanthroline- [5,6-d]imidazol-2-yl)bipyridine (mfibpy) and a tetranuclear complex in which three [Re(CO) 3 Cl] moieties are coordinated to the central Ru using the bpyC 3 bpy ligands. In the bpyC 3 bpy binuclear complexes, 4,4′-dimethyl-2,2′-bipyridine (dmb) and 4,4′-bis(trifluoromethyl)-2,2′-bipyridine ({CF 3 } 2 bpy), as well as 2,2′-bipyridine (bpy), were used as peripheral ligands on the Ru moiety. Greatly improved photocatalytic activities were obtained only in the cases of [Ru{bpyC 3 bpyRe(CO) 3 Cl} 3 ] 2+ (RuRe 3 ) and the binuclear complex [(dmb) 2 Ru(bpyC 3 bpy)Re-(CO) 3 Cl] 2+ (d 2 Ru−Re), while photocatalytic responses were extended further into the visible region. The excited state of ruthenium in all Ru−Re complexes was efficiently quenched by 1-benzyl-1,4-dihydronicotinamide (BNAH). Following reductive quenching in the case of d 2 Ru−Re, generation of the one-electron-reduced (OER) species, for which the added electron resides on the Ru-bound bpy end of the bridging ligand bpyC 3 bpy, was confirmed by transient absorption spectroscopy. The reduced Re moiety was produced via a relatively slow intramolecular electron transfer, from the reduced Ru-bound bpy to the Re site, occurring at an exchange rate (∆G ∼ 0). Electron transfer need not be rapid, since the rate-determining process is reduction of CO 2 with the OER species of the Re site. Comparison of these results with those for other bimetallic systems gives us more general architectural pointers for constructing supramolecular photocatalysts for CO 2 reduction.

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“…Although eqs – constitute a complete description of the rate of dipolar energy transfer, quantifying the donor−acceptor distance ( R ) and the orientation factor (κ 2 ) can be quite difficult, particularly in polynuclear donor−acceptor assemblies. – Taking R as the metal−metal distance is a reasonable assumption when structural data are not available, but in the point-dipole approximation of Förster theory this may or may not accurately reflect the relevant distance in systems comprised of donor and acceptor states that are charge-transfer in nature. In addition, the orientation factor of κ 2 = 2 / 3 typically invoked represents an isotropic value for species sampling all possible angular distributions .…”

Section: Introductionmentioning

confidence: 99%

Energy Transfer Dynamics in Re^I−Based Polynuclear Assemblies: A Quantitative Application of Förster Theory

et al. 2008

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The synthesis, structure, and photophysical properties of a new family of tetranuclear FeRe 3 chromophore-quencher complexes having the general form [Fe(pyacac) 3(Re(bpy')(CO) 3) 3](OTf) 3 (where pyacac = 3-(4-pyridyl)-acetylacetonate and bpy' is 4,4',5,5'-tetramethyl-2,2'-bipyridine (tmb, 1), 2,2'-bipyridine (bpy, 2), and 4,4'-diethylester-2,2'-bipyridine (deeb, 3)) are reported. Time-resolved emission data acquired in room-temperature CH 2Cl 2 solutions exhibited single exponential decay kinetics with observed lifetimes of 450 +/- 30 ps, 755 +/- 40 ps, and 2.5 +/- 0.1 ns for complexes 1, 2, and 3, respectively. The emission in each case is assigned to the decay of the Re (I)-based (3)MLCT excited state; the lifetimes are all significantly less than the corresponding AlRe 3 analogues (2250 +/- 100 ns, 560 +/- 30 ns, and 235 +/- 20 ns for 4, 5, and 6, respectively), which were also prepared and characterized. Electron transfer is found to be thermodynamically unfavorable for all three Re (I)-containing systems: this fact coupled with the absence of optical signatures for the expected charge-separated photoproducts in the time-resolved differential absorption spectra and favorable spectral overlap between the donor emission and the acceptor absorption profiles implicates dipolar energy transfer from the Re (I)-based excited state to the high-spin Fe (III) core as the dominant quenching pathway in these compounds. Details obtained from the X-ray structural data of complex 2 allowed for a quantitative application of Forster energy transfer theory by systematically calculating the separation and spatial orientation of the donor and acceptor transition moment dipoles. Deviations between the calculated and observed rate constants for energy transfer were less that a factor of 3 for all three complexes. This uncommonly high degree of precision testifies to both the appropriateness of the Forster model as applied to these systems, as well as the accuracy that can be achieved in quantifying energy transfer rates if relative dipole orientations can be accounted for explicitly.

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Competitive energy and electron-transfer quenching across the peptide-bridge in polypyridine ruthenium(II)/osmium(II) binuclear systems

Cited by 18 publications

References 16 publications

Aminoethylglycine-Functionalized Ru(bpy)₃²⁺ with Pendant Bipyridines Self-Assemble Multimetallic Complexes by Copper and Zinc Coordination

Aminoethylglycine-Functionalized Ru(bpy)₃²⁺ with Pendant Bipyridines Self-Assemble Multimetallic Complexes by Copper and Zinc Coordination

Architecture of Supramolecular Metal Complexes for Photocatalytic CO₂ Reduction: Ruthenium−Rhenium Bi- and Tetranuclear Complexes

Energy Transfer Dynamics in Re^I−Based Polynuclear Assemblies: A Quantitative Application of Förster Theory

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Competitive energy and electron-transfer quenching across the peptide-bridge in polypyridine ruthenium(II)/osmium(II) binuclear systems

Cited by 18 publications

References 16 publications

Aminoethylglycine-Functionalized Ru(bpy)32+ with Pendant Bipyridines Self-Assemble Multimetallic Complexes by Copper and Zinc Coordination

Aminoethylglycine-Functionalized Ru(bpy)32+ with Pendant Bipyridines Self-Assemble Multimetallic Complexes by Copper and Zinc Coordination

Architecture of Supramolecular Metal Complexes for Photocatalytic CO2 Reduction: Ruthenium−Rhenium Bi- and Tetranuclear Complexes

Energy Transfer Dynamics in ReI−Based Polynuclear Assemblies: A Quantitative Application of Förster Theory

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Aminoethylglycine-Functionalized Ru(bpy)₃²⁺ with Pendant Bipyridines Self-Assemble Multimetallic Complexes by Copper and Zinc Coordination

Aminoethylglycine-Functionalized Ru(bpy)₃²⁺ with Pendant Bipyridines Self-Assemble Multimetallic Complexes by Copper and Zinc Coordination

Architecture of Supramolecular Metal Complexes for Photocatalytic CO₂ Reduction: Ruthenium−Rhenium Bi- and Tetranuclear Complexes

Energy Transfer Dynamics in Re^I−Based Polynuclear Assemblies: A Quantitative Application of Förster Theory