Transient near-IR absorption spectrum in laser flash photolyzed aqueous solutions of tris(2,2′-bipyridyl) ruthenium(II)

Shimizu, Okiyasu; Watanabe, Jun; Naito, Shuichi

doi:10.1016/s0009-2614(00)01281-1

Cited by 11 publications

(20 citation statements)

References 14 publications

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“…Experimental data concerning [Ru(bpy) 3 ] 2 + , essentially in the middle-visible and IR regions, have been reported in the past. [36,37] More recently, Shimizu et al [38] have obtained the near-IR absorption, which shows a broad band (700 to 1300 nm) peaking at 900 nm. We have also commented on such data in the 400-1000 nm range for Ru-bp and Ru-L in our previous paper.…”

Section: Oxidised Ruthenium Complexesmentioning

confidence: 99%

A Theoretical Investigation into the Photophysical Properties of Ruthenium Polypyridine‐Type Complexes

Charlot

Pellegrin

Quaranta

et al. 2006

Chemistry A European J

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Excited states of ruthenium polypyridine-type complexes have always attracted the interest of chemists. We have recently found evidence of a remarkable long-lived excited state (30 micros) for a Ru(II) complex containing a heteroditopic ligand that can be viewed as a fused phenanthroline and salophen ligand.1 To unravel this intriguing electronic property, we have used density functional theory (DFT) calculations to understand the ground-state properties of [(bpy)(2)Ru(LH(2))](2+), where LH(2) represents N,N'-bis(salicylidene)-(1,10-phenanthroline)diamine. Excited singlet and triplet states have been examined by the time-dependent DFT (TDDFT) formalism and the theoretical findings have been compared with those for the parent complex [Ru(bpy)(3)](2+). The outstanding result is the presence of excited states lower in energy than the metal-to-ligand charge-transfer states, originating from intraligand charge transfer (ILCT) from the phenolic rings to the phenanthroline part of the coordinated LH(2). The spin density distribution for the lowest triplet state provides evidence that it is in fact the lowest triplet state of the free ligand. Correlation between the energy level diagram of orbitals for the ground state and that for the (3)ILCT state clearly establishes that the ruthenium retains its formal Ru(II) oxidation state. The quenching of the luminescence and the evidence of the long-lived excited state observed for [(bpy)(2)Ru(LH(2))](2+) are discussed in the light of the computational results.

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Section: Oxidised Ruthenium Complexesmentioning

confidence: 99%

A Theoretical Investigation into the Photophysical Properties of Ruthenium Polypyridine‐Type Complexes

Charlot

Pellegrin

Quaranta

et al. 2006

Chemistry A European J

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“…The injection dynamics was probed over a broad range of wavelengths. The analysis focused on the 750-1100 nm spectral region, where only the MLCT excited state of the Ru II chromophore and the electron injected into the conduction band of TiO 2 , e -TiO2 , exhibit appreciable absorption 8,9 and no stimulated emission is observed.For the reference system 1/TiO 2 the electron injection occurred within the response time of our instrument, k inj > 1 × 10 13 s -1 , and only the long-lived absorption of e -TiO2 was detected ( Figure 2a, lowest trace). This is fully consistent with the reports of other groups, which place the injection rate of directly bound Ru II -polypyridyl sensitizers in the sub-100 fs range.…”

mentioning

confidence: 99%

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confidence: 99%

Subpicosecond Photoinduced Charge Injection from “Molecular Tripods” into Mesoporous TiO₂ Over the Distance of 24 Angstroms

et al. 2003

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Sensitization processes resulting from the photoexcitation of chromophores (sensitizers) bound to semiconductor nanoparticles are of great importance for solar energy conversion. 1 Examples are TiO 2 solar cells, where the sensitizer is usually a Ru II -polypyridyl complex substituted with COOR binding groups, such as Ru(bpy) 2 -(dme) 2+ (1). 2 To study the dynamics of long-range interfacial charge-transfer processes in sensitizer/semiconductor nanoparticle systems, 3 we prepared a series of rigid sensitizers made of a tripod-shaped base terminated with a Ru II complex and attached them to the surface of mesoporous nanocrystalline (anatase) TiO 2 thin films through three COOR groups. 4 The three-point attachment and the rigidity of these molecules allow the control of the distance and orientation of the sensitizer with respect to the nanoparticle surface. Earlier nanosecond experiments with the tripod/TiO 2 systems demonstrated that the excited-state electron injection is quantitative and occurs well within the duration of the laser pulse. 4a,b In this communication, we report the observation of ultrafast charge injection from the longest tripods prepared in these laboratories, 2 and 3 shown in Figure 1, 5 in which the Ru-to-footprint distance is 24 Å. 6 To our knowledge, this is the first example of subpicosecond photoinduced ET in sensitized TiO 2 occurring over such extended distances.Interfacial charge injection was investigated in 2 and 3 ( Figure 1) bound to TiO 2 mesoporous films, with 1 serving as the reference. The structures of 2 and 3 are identical except for the ligand connecting the Ru II center to the tripod (phenanthroline in 2 and bipyridine in 3). The thin films were cast on microscope cover glasses and treated with solutions of 1, 2, or 3, following previously described procedures. 4a The resulting 1/TiO 2 , 2/TiO 2 , and 3/TiO 2 systems were excited at 405 nm (SH) and probed with the white light continuum generated by the fundamental output of a homebuilt 1 kHz multipass Ti:sapphire amplifier. 7 The typical pulse length was 110 fs, and the beams were mildly focused to ∼0.5-1.0 mm diameter at the sample. The injection dynamics was probed over a broad range of wavelengths. The analysis focused on the 750-1100 nm spectral region, where only the MLCT excited state of the Ru II chromophore and the electron injected into the conduction band of TiO 2 , e -TiO2 , exhibit appreciable absorption 8,9 and no stimulated emission is observed.For the reference system 1/TiO 2 the electron injection occurred within the response time of our instrument, k inj > 1 × 10 13 s -1 , and only the long-lived absorption of e -TiO2 was detected ( Figure 2a, lowest trace). This is fully consistent with the reports of other groups, which place the injection rate of directly bound Ru II -polypyridyl sensitizers in the sub-100 fs range. 10 Recent stateof-the-art measurements on related sensitizers show that this rate is ∼20-30 fs, 11 i.e., much faster than the duration of our excitation and probe pulses. Upon excitation...

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“…Photoionization of the starting material by a parallel route that bypasses the triplet state is highly unlikely because, on excitation of [Ru(bpy) 3 ] 2+ , the triplet state forms within 300 fs7, with a quantum yield of one 8, 9b. Because of the very high redox potential of the Ru III /Ru IV couple,10 all routes leading to [Ru(bpy) 3 ] 4+ must be discounted for thermodynamic reasons; this includes subsequent monophotonic or biphotonic ionization of [Ru(bpy) 3 ] 3+ , formed by the pathway in Scheme , as well as the ejection of two electrons from a higher excited state of the starting material, in a parallel reaction.…”

Section: Methodsmentioning

confidence: 99%

“…The ionization quantum yield ϕ ion of the MLCT triplet species is linearly related to the constant κ 2 divided by the known9a extinction coefficient ε T of *[Ru(bpy) 3 ] 2+ 6. However, to eliminate inner‐filter effects we used the excitation of [Ru(bpy) 3 ] 2+ , for which the quantum yield is one,8, 9b as a chemical actinometer, and calculated ϕ ion from the best‐fit constants κ 1 and κ 2 , ε T , and the ground‐state extinction coefficient ε G with Equation (5). In this way, we arrived at a value of 0.016±10 % for ϕ ion .…”

Section: Methodsmentioning

confidence: 99%

Near-UV Photoionization of [Ru(bpy)₃]²⁺: A Catalytic Cycle with an Excited Species as Catalyst

Goez

Schiewek

Musa

2002

Angew. Chem. Int. Ed.

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Transient near-IR absorption spectrum in laser flash photolyzed aqueous solutions of tris(2,2′-bipyridyl) ruthenium(II)

Cited by 11 publications

References 14 publications

A Theoretical Investigation into the Photophysical Properties of Ruthenium Polypyridine‐Type Complexes

A Theoretical Investigation into the Photophysical Properties of Ruthenium Polypyridine‐Type Complexes

Subpicosecond Photoinduced Charge Injection from “Molecular Tripods” into Mesoporous TiO₂ Over the Distance of 24 Angstroms

Near-UV Photoionization of [Ru(bpy)₃]²⁺: A Catalytic Cycle with an Excited Species as Catalyst

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Transient near-IR absorption spectrum in laser flash photolyzed aqueous solutions of tris(2,2′-bipyridyl) ruthenium(II)

Cited by 11 publications

References 14 publications

A Theoretical Investigation into the Photophysical Properties of Ruthenium Polypyridine‐Type Complexes

A Theoretical Investigation into the Photophysical Properties of Ruthenium Polypyridine‐Type Complexes

Subpicosecond Photoinduced Charge Injection from “Molecular Tripods” into Mesoporous TiO2 Over the Distance of 24 Angstroms

Near-UV Photoionization of [Ru(bpy)3]2+: A Catalytic Cycle with an Excited Species as Catalyst

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Subpicosecond Photoinduced Charge Injection from “Molecular Tripods” into Mesoporous TiO₂ Over the Distance of 24 Angstroms

Near-UV Photoionization of [Ru(bpy)₃]²⁺: A Catalytic Cycle with an Excited Species as Catalyst