Absorption Spectra, Photophysical Properties, and Redox Behavior of Stereochemically Pure Dendritic Ruthenium(II) Tetramers and Related Dinuclear and Mononuclear Complexes

Campagna, Sebastiano; Serroni, Scolastica; Bodige, Swamy; MacDonnell, Frederick M.

doi:10.1021/ic9811852

Cited by 119 publications

(105 citation statements)

References 73 publications

(60 reference statements)

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“…This oxidation potential is similar to that of the related tpphz dimer (+1.34 V) (Campagna et al 1999), as well as to other dinuclear ruthenium complexes containing long fully aromatic BLs (Balzani et al 1996;Bolger et al 1996;De Cola and Belser 1998). The observation of a single wave corroborates the weak electronic interaction of the two ruthenium centers, consistent with the electronic spectra.…”

Section: Electrochemistry and Spectroelectrochemistrysupporting

confidence: 83%

“…This corresponds well with p 0 (LUMO) and p 1 (LUMO+1) orbital descriptions in that the coordinating nitrogens on tatpp show little to no orbital density in p 0 but large orbital densities in p 1 , suggesting weak and strong coupling with the Ru dp (t 2g ) orbitals for p 0 and p 1 , respectively. We and others have previously used this localized description of the orbital properties/excited state electron localization as a useful way of interpreting the spectroscopic, photophysical and redox data for tatpp, tatpq, tpphz, and dppz complexes (Chambron et al 1985;Amouyal et al 1990;Fees et al 1993;Bolger et al 1996;Ishow et al 1998Ishow et al , 1999Campagna et al 1999;Chiorboli et al 1999;Flamigni et al 2000;Pourtois et al 2004). …”

Section: Assignment Of the Electronic Spectra Of P And Its Reduced Formsmentioning

confidence: 99%

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Driving Multi-electron Reactions with Photons: Dinuclear Ruthenium Complexes Capable of Stepwise and Concerted Multi-electron Reduction

et al. 2006

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Using biological precedents, it is expected that concerted, multi-electron reduction processes will play a significant role in the development of efficient artificial photosynthetic systems. We have found that the dinuclear ruthenium complexes [(phen)(2)Ru(tatpp)Ru(phen)(2)](4+) (P) and [(phen)(2)Ru(tatpq) Ru(phen)(2)](4+) (Q) undergo photodriven 2- and 4-electron reductions, respectively, in the presence of a sacrificial reductant. Importantly, these processes are completely reversible upon exposure to air, and consequently, these complexes have the potential to be used catalytically in multi-electron transfer reactions. A localized molecular orbital description of the ligands and complexes is used to explain both the function and spectroscopy of these complexes. In both complexes, the reducing equivalents are stored in the pi* orbitals of the bridging ligands and depending on the solution pH, various protonation states of the reduced species of P and Q are obtained. Under basic conditions, the photochemical pathway favors sequential single-electron reductions, while neutral or slightly acidic conditions give rise to proton-coupled multi-electron transfer. In fact, at sufficiently acidic pH, only a coupled two-electron, 2-proton process is seen. Few molecular photocatalysts are capable of proton-coupled multi-electron transfer, which is believed to be a fundamental component of light-activated energy storage in nature.

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Section: Electrochemistry and Spectroelectrochemistrysupporting

confidence: 83%

Section: Assignment Of the Electronic Spectra Of P And Its Reduced Formsmentioning

confidence: 99%

Driving Multi-electron Reactions with Photons: Dinuclear Ruthenium Complexes Capable of Stepwise and Concerted Multi-electron Reduction

et al. 2006

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“…[46] Both hexafluorophosphate salts of complexes 3 and 4 are emissive in acetonitrile, with excitation resulting in unstructured emission at 660 and 675 nm, respectively ( Table 1). The emission energy and quantum yield for 3 and 4 are comparable to the homo ruthenium(II) structural analogue, 1 (l em = 671 nm, fMLCT = 5.6 10 À3 ), [44,47] and indicate that emission from the new complexes is from a Ru II -based 3 MLCT state. As was expected from previous studies, [25,26,38] the luminescence of the new complex is also solvent dependent.…”

Section: Photophysical Propertiesmentioning

confidence: 71%

Tuning the Cellular Uptake Properties of Luminescent Heterobimetallic Iridium(III)–Ruthenium(II) DNA Imaging Probes

Wragg

Gill

Turton

et al. 2014

Chemistry A European J

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The synthesis of two new luminescent dinuclear Ir(III)-Ru(II) complexes containing tetrapyrido[3,2-a:2',3'-c:3'',2''-h:2''',3'''-j]phenazine (tpphz) as the bridging ligand is reported. Unlike many other complexes incorporating cyclometalated Ir(III) moieties, these complexes display good water solubility, allowing the first cell-based study on Ir(III)-Ru(II) bioprobes to be carried out. Photophysical studies indicate that emission from each complex is from a Ru(II) excited state and both complexes display significant in vitro DNA-binding affinities. Cellular studies show that each complex is rapidly internalised by HeLa cells, in which they function as luminescent nuclear DNA-imaging agents for confocal microscopy. Furthermore, the uptake and nuclear targeting properties of the complex incorporating cyclometalating 2-(4-fluorophenyl)pyridine ligands around its Ir(III) centre is enhanced in comparison to the non-fluorinated analogue, indicating that fluorination may provide a route to promote cell uptake of transition-metal bioprobes.

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“…From both the current data and by comparison with the related Ru II complexes of dipyridophenazine (dppz) [31][32][33][34][35][36][37][38][39] and tetrapyridophenazine (tpphz), [28,32,40,41] it is clear that complex P can be viewed as three weakly coupled molecular components; the two independent "Ru II -trisbipyridine" chromophores and a central tetraazapenacene acceptor unit to form a chromophore-acceptor-chromophore triad. The additive nature of the absorption spectra for all three components, observed in Figure 1, reflects this nature.…”

Section: Discussionmentioning

confidence: 88%

Influence of pH on the Photochemical and Electrochemical Reduction of the Dinuclear Ruthenium Complex, [(phen)₂Ru(tatpp)Ru(phen)₂]Cl₄, in Water: Proton‐Coupled Sequential and Concerted Multi‐Electron Reduction

Tacconi

Lezna

Konduri

et al. 2005

Chemistry A European J

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The dinuclear ruthenium complex [(phen)2Ru(tatpp)Ru(phen)2]4+ (P; in which phen is 1,10-phenanthroline and tatpp is 9,11,20,22-tetraaza tetrapyrido[3,2-a:2'3'-c:3'',2''-l:2''',3''']-pentacene) undergoes a photodriven two-electron reduction in aqueous solution, thus storing light energy as chemical potential within its structure. The mechanism of this reduction is strongly influenced by the pH, in that basic conditions favor a sequential process involving two one-electron reductions and neutral or slightly acidic conditions favor a proton-coupled, bielectronic process. In this complex, the central tatpp ligand is the site of electron storage and protonation of the central aza nitrogen atoms in the reduced products is observed as a function of the solution pH. The reduction mechanism and characterization of the rich array of products were determined by using a combination of cyclic and AC voltammetry along with UV-visible reflectance spectroelectrochemistry experiments. Both the reduction and protonation state of P could be followed as a function of pH and potential. From these data, estimates of the various reduced species' pKa values were obtained and the mechanism to form the doubly reduced, doubly protonated complex, [(phen)2Ru(H2tatpp)Ru(phen)2]4+ (H2P) at low pH (< or =7) could be shown to be a two-proton, two-electron process. Importantly, H2P is also formed in the photochemical reaction with sacrificial reducing agents, albeit at reduced yields relative to those at higher pH.

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Absorption Spectra, Photophysical Properties, and Redox Behavior of Stereochemically Pure Dendritic Ruthenium(II) Tetramers and Related Dinuclear and Mononuclear Complexes

Cited by 119 publications

References 73 publications

Driving Multi-electron Reactions with Photons: Dinuclear Ruthenium Complexes Capable of Stepwise and Concerted Multi-electron Reduction

Driving Multi-electron Reactions with Photons: Dinuclear Ruthenium Complexes Capable of Stepwise and Concerted Multi-electron Reduction

Tuning the Cellular Uptake Properties of Luminescent Heterobimetallic Iridium(III)–Ruthenium(II) DNA Imaging Probes

Influence of pH on the Photochemical and Electrochemical Reduction of the Dinuclear Ruthenium Complex, [(phen)₂Ru(tatpp)Ru(phen)₂]Cl₄, in Water: Proton‐Coupled Sequential and Concerted Multi‐Electron Reduction

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Absorption Spectra, Photophysical Properties, and Redox Behavior of Stereochemically Pure Dendritic Ruthenium(II) Tetramers and Related Dinuclear and Mononuclear Complexes

Cited by 119 publications

References 73 publications

Driving Multi-electron Reactions with Photons: Dinuclear Ruthenium Complexes Capable of Stepwise and Concerted Multi-electron Reduction

Driving Multi-electron Reactions with Photons: Dinuclear Ruthenium Complexes Capable of Stepwise and Concerted Multi-electron Reduction

Tuning the Cellular Uptake Properties of Luminescent Heterobimetallic Iridium(III)–Ruthenium(II) DNA Imaging Probes

Influence of pH on the Photochemical and Electrochemical Reduction of the Dinuclear Ruthenium Complex, [(phen)2Ru(tatpp)Ru(phen)2]Cl4, in Water: Proton‐Coupled Sequential and Concerted Multi‐Electron Reduction

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Influence of pH on the Photochemical and Electrochemical Reduction of the Dinuclear Ruthenium Complex, [(phen)₂Ru(tatpp)Ru(phen)₂]Cl₄, in Water: Proton‐Coupled Sequential and Concerted Multi‐Electron Reduction