Designing Dendrimers Based on Transition-Metal Complexes. Light-Harvesting Properties and Predetermined Redox Patterns

Balzani, Vincenzo; Campagna, Sebastiano; Denti, Gianfranco; Juris, Alberto; Serroni, Scolastica; Venturi, Margherita

doi:10.1021/ar950202d

“…[Ru(bpy) 3 ] 2+ , where bpy is 2,2′-bipyridine, can be considered the prototype of this class of compounds. Their extensive use in settings ranging from light harvesting in dendritic polymers 5 to the sensitization of wide band-gap semiconductors 3a testifies to the important role such compounds continue to play in molecular solar energy research. [Ru(bpy) 3 ] 2+ therefore provides the natural starting point for the study of ultrafast dynamics in inorganic charge-transfer complexes.…”

Section: The Prototype: [Ru(bpy) 3 ] 2+mentioning

confidence: 99%

Femtosecond Absorption Spectroscopy of Transition Metal Charge-Transfer Complexes

McCusker

¹

2003

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Our research is concerned with the application of femtosecond time-resolved absorption techniques to the study of the photophysics of transition metal complexes. The focus is to understand the events that characterize the process of excited-state evolution from the time a photon is absorbed by a molecule to the formation of the lowest-energy excited state of the system. This Account describes our initial observations in this area and includes examples detailing these dynamics as they occur in the charge-transfer excited states of transition-metal polypyridyl chromophores.

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“…[Ru(bpy) 3 ] 2+ , where bpy is 2,2′-bipyridine, can be considered the prototype of this class of compounds. Their extensive use in settings ranging from light harvesting in dendritic polymers 5 to the sensitization of wide band-gap semiconductors 3a testifies to the important role such compounds continue to play in molecular solar energy research. [Ru(bpy) 3 ]…”

Section: The Prototype: [Ru(bpy) 3 ] 2+mentioning

confidence: 99%

Femtosecond Absorption Spectroscopy of Transition Metal Charge‐Transfer Complexes

McCusker

¹

2004

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Our research is concerned with the application of femtosecond time-resolved absorption techniques to the study of the photophysics of transition metal complexes. The focus is to understand the events that characterize the process of excited-state evolution from the time a photon is absorbed by a molecule to the formation of the lowest-energy excited state of the system. This Account describes our initial observations in this area and includes examples detailing these dynamics as they occur in the charge-transfer excited states of transition-metal polypyridyl chromophores.

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“…Diffusion on a disordered Cayley tree with a linear potential is investigated analytically. At low temperatures we predict a phase in which the MFPT is dominated by a few paths.Dendrimers constitute a new class of nanomaterials with unusual tree-like geometry and interesting chemical, transport, and optical properties [1][2][3][4][5]. Two families of Phenylacetylene dendrimers have received considerable recent attention.…”

mentioning

confidence: 99%

Excitonic Funneling in Extended Dendrimers with Nonlinear and Random Potentials

Raychaudhuri

¹

,

Shapir

²

,

Chernyak

³

et al. 2000

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The mean first passage time (MFPT) for photoexcitations diffusion in a funneling potential of artificial tree-like light-harvesting antennae (phenylacetylene dendrimers with generation-dependent segment lengths) is computed. Effects of the non-linearity of the realistic funneling potential and slow random solvent fluctuations considerably slow down the center-bound diffusion beyond a temperature-dependent optimal size. Diffusion on a disordered Cayley tree with a linear potential is investigated analytically. At low temperatures we predict a phase in which the MFPT is dominated by a few paths.Dendrimers constitute a new class of nanomaterials with unusual tree-like geometry and interesting chemical, transport, and optical properties [1][2][3][4][5]. Two families of Phenylacetylene dendrimers have received considerable recent attention. In the compact family, the length of the linear segments is fixed, whereas in the extended family it increases towards the center creating an energy funnel in that direction (Fig. 1). This latter family may, therefore, serve as artificial light-harvesting antennas, as has been demonstrated experimentally [6]. It has been conjectured by Kopelman et. al., based on optical absorption spectra [1], that electronic excitations in these dendrimers are localized on the linear segments. This has been confirmed in theoretical studies which showed that the relative motion of photogenerated electron-hole pairs is confined to the various segments and energy-transfer may then be described by the Frenkel exciton model. The time it takes for an excitation that starts at the periphery to reach the center, and its dependence on the molecular size (number of generations g) and the funneling force, were calculated. The latter results from the interplay of entropic (or geometric, i.e. the branching ratio c = 2) and energetic factors [7].These pioneering studies, however, assumed the funneling force to be constant since the energy ǫ(n) varied linearly with n. (n=1,2,. . . ,g is the generation number, at which the segment length is l = g − n + 1 monomers. See Fig. 1.) In addition, ε(n) were assumed to be fixed. In reality, interactions with other degrees of freedom (solvent and intramolecular vibrations), induce fluctuations in ε(n) which may span many different timescales. Here we consider slow (quenched) fluctuations compared with the exciton trapping times which are typically in the picosecond range [6,8]. Nonlinear [9] and single molecule [10] spectroscopy in liquids, glasses and proteins typically show nanosecond to millisecond bath motions responsible for spectral diffusion. Slow vibrational motions that can be treated as static disorder dominate the photoinduced energy transfer dynamics of photosynthetic antenna complexes [11]. Fast (annealed) fluctuations do not change the behavior qualitatively. In addition, we explore different degrees of correlations among the various energy fluctuations. In the absence of correlations, we obtain the standard diagonal disorder (random energy) model. If the e...

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Designing Dendrimers Based on Transition-Metal Complexes. Light-Harvesting Properties and Predetermined Redox Patterns

Cited by 903 publications

References 36 publications

Femtosecond Absorption Spectroscopy of Transition Metal Charge-Transfer Complexes

Femtosecond Absorption Spectroscopy of Transition Metal Charge-Transfer Complexes

Femtosecond Absorption Spectroscopy of Transition Metal Charge‐Transfer Complexes

Excitonic Funneling in Extended Dendrimers with Nonlinear and Random Potentials

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