Temperature dependence of the photophysical and photochemical properties of the tris(2,2'-bipyridyl)ruthenium(II) ion in aqueous solution

Houten, Judith Van; Watts, Richard J.

doi:10.1021/ja00432a028

Cited by 837 publications

(672 citation statements)

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“…Rhodamine-B and Ru(bpy)3Cl2 were used as references for correction of the detector sensitivity and for determination of the fluorescence quantum yields. 30,31 Each compound studied was 85 excited at the wavelength of its absorption maximum or at the isosbestic points of titrations. Luminescence spectra were corrected for detector sensitivity.…”

Section: Instruments and Proceduresmentioning

confidence: 99%

Equilibrium, photophysical and photochemical examination of anionic lanthanum(iii) mono- and bisporphyrins: the effects of the out-of-plane structure

2012

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Lanthanum(III) ion forms kinetically labile complexes with the 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin anion (H2TSPP 4-), the compositions and formation constants of which significantly depend on the presence of potential axial ligands (at 0.01 M). Deviating from the chloride ion, acetate coordinating to the metal center hinders the formation of bisporphyrin complex. In these 10 lanthanum(III) complexes, the metal center, due to its large ionic radius (103.2 pm), is located out of the ligand plane, distorting it. Accordingly, the absorption and fluorescence spectra of these coordination compounds display special properties characteristic of the so-called sitting-atop (SAT) or out-of-plane (OOP) porphyrin complexes. Metalation significantly decreases the quantum yield of the fluorescence from the S1 excited state. Quantum chemical calculations (DFT) confirm the considerable OOP 15 displacement of the La(III) center (about 120 pm in the monoporphyrin complexes). The monoporphyrins display efficient fluorescence (0.03), while the bisporphyrin does not emit. Differing from the normal (in-plane) metalloporphyrins, excitation of these lanthanum(III) porphyrins leads to an irreversible ligandto-metal charge transfer (LMCT) followed by the opening of the porphyrin ring, which is also typical of OOP complexes. Dissociation releasing free-base porphyrin can also be observed upon irradiation of the 20 monoporphyrin in acetate solution, while in the presence of chloride ions interconversions of the monoand bisporphyrins may also take place beside the irreversible photoredox reaction.

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Section: Instruments and Proceduresmentioning

confidence: 99%

Equilibrium, photophysical and photochemical examination of anionic lanthanum(iii) mono- and bisporphyrins: the effects of the out-of-plane structure

2012

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“…On the basis of a pK a of 1.12, at pH 5, g99.99% of the complex is present as Ru(bpy) 2 (dpp) 2+ , and the emission spectrum consists of only the 705 nm emission from the unprotonated complex. Taking the quantum efficiency of emission from room temperature, 22 ( 1°C, N 2 saturated, aqueous solutions of Ru(bpy) 3 2+ in water (6) to be 0.0429 (averaged from several references 18 ), the gradient method using a series of concentrations e0.10M 11 yields 1.98 ( 0.20 × 10 -3 as the quantum efficiency of the 705 nm emission from the unprotonated complex Ru(bpy) 2 (dpp) 2+ , designated Φ em u . The 735 nm emission from the protonated complex was then measured from a deaerated, aqueous solution containing the same concentration of Ru(bpy) 2 (dpp) 2+ but 1.0 M in HNO 3 .…”

Section: Nm Emissionmentioning

confidence: 99%

Excited-State Coordination Chemistry: Excited-State Basicity of Bis(2,2′-bipyridyl)(2,3-dipyridylpyrazine)ruthenium(II)

2009

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The proton dependencies of the absorption and emission spectra of bis(2,2′-bipyridyl)(2,3-bis(2-pyridyl)pyrazine)ruthenium(II), (bpy) 2 Ru(dpp) 2+ indicate that population of the dpp-localized MLCT state increases the basicity of dpp peripheral nitrogens. NMR spectra reveal the protonation of the peripheral dpp pyridine in the ground state, pK a of 1.12 ( 0.03, occurs intermediate between the changes evident in the absorption and emission spectra. As a result, the emissivity of aqueous solutions of (bpy) 2 Ru(dpp) 2+ as a function of [H + ] derives from two emissive species: the unprotonated complex and the monoprotonated complex [(bpy) 2 Ru(dppH py )] 3+ with the proton attached to the peripheral dpp pyridine. Although protonation in the MLCT state generally quenches the emission, the emissivity of the monoprotonated complex, albeit weak, is attributed to the asymmetric distribution of the charge in the MLCT state. The majority of the transferred charge resides at the peripheral pyrazinyl nitrogen, and excited-state acid-base chemistry occurs predominantly at this site. Nonetheless, ground-state protonation of the peripheral dpp pyridine dramatically increases the nonradiative decay rate and significantly influences subsequent excited-state protonation processes. Protonation of the excited state changes from a bimolecular process to a combination of inter-and intramolecular processes where the proton transfers from the dpp pyridyl nitrogen to the dpp pyrazinyl nitrogen and from the surrounding aqueous solvent shell. Energetically, changes in the absorption spectra originally attributed to the first protonation of the complex and from which the ∆pK a of the excited state have been estimated, in fact, correspond to the second protonation of the complex. IntroductionThe hydrogen ion dependencies of the absorption and emission spectra of Ru(II) diimines reveal substantial differences in the acid-base properties of the ground and emissive MLCT states of the complexes. 1 Depending on the direction of the charge transfer relative to the acid-base site, and the location of the acceptor orbital in the MLCT state, excitation changes electron distribution, which in turn increases or decreases acid-base properties by as much as 5 to 6 orders of magnitude. 2 Brønsted basicity usually does not correlate with the coordinating ability of a ligand, but, with diimine ligands, the equilibrium constant for coordination increases linearly with the Brønsted basicity of the ligand's coordinating nitrogens. 3 Work in this laboratory focuses on whether these photoinduced changes in acid-base properties translate into an excited-state coordination chemistry where a Ru(II) diimine possessing one or more acid-base sites on the ligand periphery functions as a ligand and whether excitation enhances or reduces its ability to coordinate to another metal.Excited-state coordination chemistry arises from the observation that excitation of bis(2,2′-bipyridyl)(2,3-dipyridylpyrazine)ruthenium(II), (bpy) 2 Ru(dpp) 2+ , in the presence of PtCl 6

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“…The phosphorescence quantum yields (ϕ Ph ) for chlorins 5 and 6 were obtained by using tris(2,2′-bipyridyl)ruthenium(II) in water (ϕ F = 0.042) 25 as standard. For further details please see the experimental section in SI.…”

mentioning

confidence: 99%

Platinum(II) Ring-Fused Chlorins as Near-Infrared Emitting Oxygen Sensors and Photodynamic Agents

Pereira

Laranjo

Casalta-Lopes

et al. 2017

ACS Med. Chem. Lett.

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Novel near-infrared luminescent compounds based on platinum(II) 4,5,6,7-tetrahydropyrazolo[1,5-a]-pyridine-fused chlorins are described. These compounds have high photostability and display light emission, in particular simultaneous fluorescence and phosphorescence emission in solution at room temperature, in the biologically relevant 700−850 nm red and near-infrared (NIR) spectral region, making them excellent materials for biological imaging. The simultaneous presence of fluorescence and phosphorescence emission at room temperature, with the phosphorescence strongly quenched by oxygen whereas fluorescence remains unaffected, allows these compounds to be used as ratiometric oxygen sensors in chemical and biological media. Both steady-state (fluorescence vs phosphorescence intensities) and dynamic (dependence of phosphorescence lifetimes upon oxygen concentration) luminescence approaches can be used. Photocytotoxicity studies against human melanocytic melanoma cells (A375) indicate that these compounds display potential as photosensitizers in photodynamic therapy.

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Temperature dependence of the photophysical and photochemical properties of the tris(2,2'-bipyridyl)ruthenium(II) ion in aqueous solution

Cited by 837 publications

References 13 publications

Equilibrium, photophysical and photochemical examination of anionic lanthanum(iii) mono- and bisporphyrins: the effects of the out-of-plane structure

Equilibrium, photophysical and photochemical examination of anionic lanthanum(iii) mono- and bisporphyrins: the effects of the out-of-plane structure

Excited-State Coordination Chemistry: Excited-State Basicity of Bis(2,2′-bipyridyl)(2,3-dipyridylpyrazine)ruthenium(II)

Platinum(II) Ring-Fused Chlorins as Near-Infrared Emitting Oxygen Sensors and Photodynamic Agents

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