Mechanistic Insight into the Electronic Influences Imposed by Substituent Variation in Polyazine‐Bridged Ruthenium(II)/Rhodium(III) Supramolecules

White, Travis A.; Mallalieu, Hannah E.; Wang, Jing; Brewer, Karen J.

doi:10.1002/chem.201402564

Cited by 7 publications

(15 citation statements)

References 51 publications

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“…This behavior, in which the first reduction is ligand-localized but a second reduction yields Rh(I) and the neutral bridging ligand is known for bimetallic Rh(III) and Ir(III) complexes in which [M III ( BL – )M III ] + e – → [M III (BL 0 ) M I ] . A two-step reduction was observed for Ru,Rh bimetallic complexes with the ratios of current for each step dependent on the rate of halide dissociation . In contrast, our chloride detection experiments verify the stability of the Rh(III) coordination environment in the singly reduced species.…”

Section: Resultssupporting

confidence: 57%

“…79 A two-step reduction was observed for Ru,Rh bimetallic complexes with the ratios of current for each step dependent on the rate of halide dissociation. 80 In contrast, our chloride detection experiments verify the stability of the Rh(III) coordination environment in the singly reduced species. Wave F (−1.04 V) is assigned to the (μ-Ru,Rh I -dpp) 0/− couple of the Rh(I) complex by comparison to the nonbridging ligand potential of Ru 3 while two C waves (−1.16, −1.32 V) are assigned as the second reductions of the (μ-Ru,Ru-dpp) ligands similarly to Ru 3 .…”

Section: ■ Results and Discussionmentioning

confidence: 63%

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Tetra- and Heptametallic Ru(II),Rh(III) Supramolecular Hydrogen Production Photocatalysts

2017

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Supramolecular mixed metal complexes combining the trimetallic chromophore [{(bpy)Ru(dpp)}Ru(dpp)] (Ru) with [Rh(bpy)Cl] or [RhCl] catalytic fragments to form [{(bpy)Ru(dpp)}Ru(dpp)RhCl(bpy)](PF) (RuRh) or [{(bpy)Ru(dpp)}Ru(dpp)]RhCl(PF) (RuRhRu) (bpy = 2,2'-bipyridine and dpp = 2,3-bis(2-pyridyl)pyrazine) catalyze the photochemical reduction of protons to H. This first example of a heptametallic Ru,Rh photocatalyst produces over 300 turnovers of H upon photolysis of a solution of acetonitrile, water, triflic acid, and N,N-dimethylaniline as an electron donor. In contrast, the tetrametallic RuRh produces only 40 turnovers of H due to differences in the excited state properties and nature of the catalysts upon reduction as ascertained from electrochemical data, transient absorption spectroscopy, and flash-quench experiments. While the lowest unoccupied molecular orbital of RuRh is localized on a bridging ligand, it is Rh-centered in RuRhRu facilitating electron collection at Rh in the excited state and reductively quenched state. The Ru → Rh charge separated state of RuRhRu is endergonic with respect to the emissive Ru → dpp MLCT excited and cannot be formed by static electron transfer quenching of theMLCT state. Instead, a mechanism of subnanosecond charge separation from high lying states is proposed. Multiple reductions of Ru and RuRh using sodium amalgam were carried out to compare UV-vis absorption spectra of reduced species and to evaluate the stability of highly reduced complexes. The Ru and RuRh can be reduced by 10 and 13 electrons, respectively, to final states with all bridging ligands doubly reduced and all bpy ligands singly reduced.

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Section: Resultssupporting

confidence: 57%

Section: ■ Results and Discussionmentioning

confidence: 63%

Tetra- and Heptametallic Ru(II),Rh(III) Supramolecular Hydrogen Production Photocatalysts

2017

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“…The reductive properties of the Ru(II),Rh(III) bimetallics (Figure ) are considerably more complex than the Ru(II) monometallic counterparts, expected to possess dpp 0/– and Rh III/II and Rh II/I reductions prior to bpy 0/– reductions. Three separate reduction processes, −0.38, −0.72, and −0.99 V vs Ag/AgCl, are observed and attributed to Rh III/II , Rh II/I , and dpp 0/– reductions, demonstrating the energetic proximity of the Rh(dσ*) and dpp(π*) orbitals in this bimetallic motif. − To confirm the assignment of these reduction processes, a study was performed by White et al using a set of nearly identical Ru(II),Rh(III) bimetallics, differing only in the terminal ligands . It was found that the first two reductions displayed electrochemical irreversibility, indicating an electrochemical reduction followed by rapid halide loss.…”

Section: Resultsmentioning

confidence: 98%

“…58−60 To confirm the assignment of these reduction processes, a study was performed by White et al using a set of nearly identical Ru(II),Rh(III) bimetallics, differing only in the terminal ligands. 61 It was found that the first two reductions displayed electrochemical irreversibility, indicating an electrochemical reduction followed by rapid halide loss. The irreversibility of these Rh III/II and Rh II/I also varies with potential scan rate, providing mechanistic insight into the systems.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Tuning the Photophysical Properties of Ru(II) Monometallic and Ru(II),Rh(III) Bimetallic Supramolecular Complexes by Selective Ligand Deuteration

et al. 2015

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A series of three new complexes of the design [(TL)2Ru(BL)](2+), two new complexes of the design [(TL)2Ru(BL)Ru(TL)2](4+), and three new complexes of the design [(TL)2Ru(BL)RhCl2(TL)](3+) (TL = bpy or d8-bpy; BL = dpp or d10-dpp; TL = terminal ligand; BL = bridging ligand; bpy = 2,2'-bipyridine; dpp = 2,3-bis(2-pyridyl)pyrazine) were synthesized and the (1)H NMR spectroscopy, electrochemistry, electronic absorbance spectroscopy, and photophysical properties studied. Incorporation of deuterated ligands into the molecular architecture simplifies the (1)H NMR spectra, allowing for complete (1)H assignment of [(d8-bpy)2Ru(dpp)](PF6)2 and partial assignment of [(bpy)2Ru(d10-dpp)](PF6)2. The electrochemistry for the deuterated and nondeuterated species showed nearly identical redox properties. Electronic absorption spectroscopy of the deuterated and nondeuterated complexes are superimposable with the lowest energy transition being Ru(dπ) → BL(π*) charge transfer in nature (BL = dpp or d10-dpp). Ligand deuteration impacts the excited-state properties with an observed increase in the quantum yield of emission (Φ(em)) and excited-state lifetime (τ) of the Ru(dπ) → d10-dpp(π*) triplet metal-to-ligand charge transfer ((3)MLCT) excited state when dpp is deuterated, and a decrease in the rate constant for nonradiative decay (knr). Choice of ligand deuteration between bpy and dpp strongly impacts the observed photophysical properties with BL = d10-dpp complexes showing an enhanced Φ(em) and τ, providing further support that the lowest electronic excited state populated via UV or visible excitation is the photoactive Ru(dπ) → dpp(π*) CT excited state. The Ru(II),Rh(III) complex incorporating the deuterated BL shows increased hydrogen production compared to the variants incorporating the protiated BL, while demonstrating identical dynamic quenching behaviors in the presence of sacrificial electron donor.

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“…Synthesis of Ru II ‐Rh III : [(phen) 2 Ru(dpp)RhCl 2 (phen)](PF 6 ) 3 was synthesized through a building block approach (Scheme S1) based on previously reported methods for Ru II ,Rh III bimetallics modified as follows . [RhCl 3 (phen)(DMF)] (60.9 mg, 0.132 mmol) was dissolved in warm ethanol/water 2:1 (10 mL), and a solution of [(phen) 2 Ru(dpp)](PF 6 ) 2 (110 mg, 0.112 mmol) in the same solvent mixture (10 mL) was added slowly.…”

Section: Methodsmentioning

confidence: 99%

Mechanistic Investigation into DNA Modification by a Ru^II,Rh^III Bimetallic Complex

et al. 2018

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Despite significant progress in the treatment of cancer, there remains an urgent need for more effective therapies that also have less impact on patient wellbeing. Photodynamic therapy employs targeted light activation of a photosensitizer in selected tissues, thereby reducing off-target toxicity. Our group previously reported a Ru ,Rh bimetallic architecture that displays multifunctional covalent photomodification of DNA in the therapeutic window in an oxygen-independent manner, features that are essential for treating deep and hypoxic tumors. Herein, we explore the mechanism by which a new analogue, [(phen) Ru(dpp)Rh(phen)Cl ] , or Ru -Rh , interacts with DNA. We established that Ru -Rh exhibits "light switch" behavior in the presence of DNA, undergoing strong electrostatic interactions that might involve groove binding. Furthermore, these noncovalent interactions play a major role in the covalent photobinding and photocleavage of DNA, which occur according to an oxygen-independent mechanism. Polymerase chain reaction (PCR) revealed that covalent modification of DNA by Ru -Rh , especially photobinding, is critical to inhibiting amplification, thus suggesting that the complex could exert its toxic activity by interfering with DNA replication in cells. This new structural motif, with phenanthroline at all three terminal ligand positions, has a number of properties that are promising for the continued refinement of photodynamic-therapy strategies.

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Mechanistic Insight into the Electronic Influences Imposed by Substituent Variation in Polyazine‐Bridged Ruthenium(II)/Rhodium(III) Supramolecules

Cited by 7 publications

References 51 publications

Tetra- and Heptametallic Ru(II),Rh(III) Supramolecular Hydrogen Production Photocatalysts

Tetra- and Heptametallic Ru(II),Rh(III) Supramolecular Hydrogen Production Photocatalysts

Tuning the Photophysical Properties of Ru(II) Monometallic and Ru(II),Rh(III) Bimetallic Supramolecular Complexes by Selective Ligand Deuteration

Mechanistic Investigation into DNA Modification by a Ru^II,Rh^III Bimetallic Complex

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Mechanistic Insight into the Electronic Influences Imposed by Substituent Variation in Polyazine‐Bridged Ruthenium(II)/Rhodium(III) Supramolecules

Cited by 7 publications

References 51 publications

Tetra- and Heptametallic Ru(II),Rh(III) Supramolecular Hydrogen Production Photocatalysts

Tetra- and Heptametallic Ru(II),Rh(III) Supramolecular Hydrogen Production Photocatalysts

Tuning the Photophysical Properties of Ru(II) Monometallic and Ru(II),Rh(III) Bimetallic Supramolecular Complexes by Selective Ligand Deuteration

Mechanistic Investigation into DNA Modification by a RuII,RhIII Bimetallic Complex

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Mechanistic Investigation into DNA Modification by a Ru^II,Rh^III Bimetallic Complex