Aggregation in Fluid Solution of Dendritic Supermolecules made of Ruthenium(II)- and Osmium(II)-Polypyridine Building Blocks

Campagna, Sebastiano; Giannetto, Antonino; Serroni, Scolastica; Denti, Gianfranco; Trusso, S.; Mallamace, Francesco; Micali, Norberto

doi:10.1021/ja00111a012

Cited by 47 publications

(23 citation statements)

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“…There are several possibilities as to why H 2 P does not fully form at lower pH including: 1) pH-induced aggregation which alters the photophysical behavior, 2) protonation events that deactivate the photoexcited state of the complex in a non-productive manner, and/or 3) the Ru chromophores and the TEOA reducing agent are unable to deliver two electrons simultaneously. Aggregation of these [25] and related types of complexes [20,[26][27][28][29][30] is well established and has been observed to alter some physical properties. We have yet to systematically determine the effects of aggregation and electron stoichiometry but note that these effects may be addressable by synthetic modification of the structure (e.g., covalently tethering donor units to the Ru chromophores; overall charge modification).…”

Section: Electrochemistry and Spectroelectrochemistry Of P In Watermentioning

confidence: 99%

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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Section: Electrochemistry and Spectroelectrochemistry Of P In Watermentioning

confidence: 99%

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 heavy-atom effect induces strong spin-orbit coupling and makes intersystem crossing (ISC) extremely fast. [27][28][29][30][31][32][33][34][35][36][37][38][39] As a consequence, very fast light-induced population of the lowestlying excited state occurs without regard of its multiplicity; for example, in the case of Ru II -and Os II -polypyridine complexes, the lowest-lying metal-to-ligand charge-transfer triplet state ( 3 MLCT) is produced on the sub-picosecond timescale and with unitary efficiency from the 1 MLCT level, initially prepared by light irradiation. [40][41][42][43][44] Therefore, in the design of dendrimer systems based on transition-metal polypyridine complexes, information about the driving force for fundamental processes, such as intercomponent photoinduced electron and energy transfer, are obtained by considering the triplet-state energy of the metal-atom components.…”

Section: Introductionmentioning

confidence: 99%

Extending the Light‐Harvesting Properties of Transition‐Metal Dendrimers

et al. 2007

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We report a study of the electronic energy-transfer dynamics within the transition-metal polypyridine complex OsRu3pyr6 (Os[(dpp)Ru(bpy{pyrene})2]3(8+), where dpp=2,3-bis(2'-pyridyl)pyrazine and bpy=2,2'-bipyridine) after excitation with UV light. By using a broadband visible femtosecond probe, we are able to simultaneously detect both the energy transfer from the peripheral aromatic ligands to the Os center and the sub-picosecond energy transfer from the initially excited Ru-bpy ligand-centered state to the Os triplet metal-to-ligand charge-transfer (MLCT) state. Pyrene energy transfer occurs from both the nonrelaxed and the relaxed S(1) states on timescales of 6 and 45 ps, respectively. In both cases, the energy transfer is described by means of Förster energy transfer theory. Sub-picosecond energy transfer within the OsRu3 metal-ligand core most likely includes a direct energy transfer between the higher-lying ligand-centered states on Ru and Os, in addition to the transfer between the MLCT states. The absorption cross-sections in both the UV and the visible spectral regions are enhanced by attaching the aromatic pyrene ligands. Furthermore, energy transfer is directed only towards the Os core, which ultimately leads to an exclusive population of the Os-based triplet MLCT state, thus making the OsRu3pyr6 transition metal-polypyridine dendrimer an obvious candidate for artificial light-harvesting systems.

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“…These special structure and properties are drawing more and more attentions on HBPs in the fields of catalysts, [1][2][3] organic nanoparticles, [4][5][6] ultra thin films, [7,8] etc. Concerning the synthesis efficiency, one of the reasonable exploration trends is to fabricate larger-matrix materials with novel properties using HBPs (especially for those in sticky states).…”

Section: Introductionmentioning

confidence: 99%

Novel Cross‐Linked Films Prepared from Hyperbranched Poly(amine‐ester)

Wei

Zhu

Xiao

et al. 2005

Macromol. Rapid Commun.

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Summary: Novel hyperbranched poly(amine‐ester) (HPAE) cross‐linked films were prepared by cross‐linking the terminal hydroxyl groups of HPAE using glutaraldehyde (GA). Atom force microscope and scanning electron microscope revealed their smooth surfaces, dense and homogenous matrices. Property characterizations indicated that these cross‐linked films had good hydrophilicity, relative low protein adsorption, and high tensile strength. Also, their swelling behavior varied with the solvent.Structure of the hyperbranched poly(amine‐ester).magnified imageStructure of the hyperbranched poly(amine‐ester).

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Aggregation in Fluid Solution of Dendritic Supermolecules made of Ruthenium(II)- and Osmium(II)-Polypyridine Building Blocks

Cited by 47 publications

References 0 publications

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

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

Extending the Light‐Harvesting Properties of Transition‐Metal Dendrimers

Novel Cross‐Linked Films Prepared from Hyperbranched Poly(amine‐ester)

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Aggregation in Fluid Solution of Dendritic Supermolecules made of Ruthenium(II)- and Osmium(II)-Polypyridine Building Blocks

Cited by 47 publications

References 0 publications

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

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

Extending the Light‐Harvesting Properties of Transition‐Metal Dendrimers

Novel Cross‐Linked Films Prepared from Hyperbranched Poly(amine‐ester)

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Product

Resources

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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

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