Multiple emissions from charge transfer excited states of ruthenium(II)—polypyridine complexes

Sullivan, B. Patrick; Abruña, Héctor D.; Finklea, Harry O.; Salmon, Dennis J.; Nagle, Jeffrey K.; Meyer, Thomas J.; Sprintschnik, Hertha W.

doi:10.1016/0009-2614(78)85059-3

Cited by 47 publications

(20 citation statements)

References 29 publications

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“…When methyl groups are attached to the qtpy ligands, complexes 10 , 11 , and 12 emit appreciably more weakly in acetonitrile ( Φ em =0.013, Φ em =0.013, and Φ em =0.033, respectively) than their unmethylated analogs, but are not completely quenched, with emission being red‐shifted; these observations are consistent with the incorporation of electron accepting pyridinium groups and similar behavior has been reported for related complexes 17. 19b Interestingly, again, the complex that contains dppz ligands, 12 , shows anomalous behavior.…”

Section: Resultssupporting

confidence: 82%

“…[24] As with their ruthenium analogs, and consistent with reports on related systems, [25] N-methylation results in luminescence red-shifts of around 20 nm and an appreciable decrease in emission intensity. This arises from the replacement of a p-donating halide ligand with a p-accepting acetonitrile ligand; previous studies by Guarr and co-workers reveal similar effects for related Re Ibased complexes.…”

Section: Spectral Studiessupporting

confidence: 87%

“…This arises from the replacement of a p-donating halide ligand with a p-accepting acetonitrile ligand; previous studies by Guarr and co-workers reveal similar effects for related Re Ibased complexes. [24] As with their ruthenium analogs, and consistent with reports on related systems, [25] N-methylation results in luminescence red-shifts of around 20 nm and an appreciable decrease in emission intensity.…”

Section: Spectral Studiessupporting

confidence: 87%

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Tuning the Excited State of Photoactive Building Blocks for Metal‐Templated Self‐Assembly

Ahmad

Meijer

Thomas

2011

Chemistry An Asian Journal

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The reaction of 2,2':4,4'':4',4'''-quaterpyridyl (qtpy), with d(6) ruthenium(II) (Ru(II) ), and rhenium(I) (Re(I) ) metal centers has been investigated. The pendant pyridyl groups on the products have also been methylated to produce a second series of complexes containing coordinated Meqtpy(2+). The absorption spectra of the complexes are dominated by intraligand and charge-transfer bands. The ruthenium(II) complexes display broad unstructured luminescence consistent with emission from a Ru(d)→diimine(π*) manifold in acetonitrile solutions. In aqueous solutions, their emissions are weaker and the lifetimes are shorter. This effect is particularly acute for complexes incorporating coordinated dipyridylpyrazine, dppz, ligands. Although the emission of the ruthenium(II) complexes containing Meqtpy(2+) is generally shorter than their qtpy analogs, it is notable that solvent-dependent effects are much less intense. The rhenium(I) complexes also display broad unstructured luminescence but, compared with the ruthenium(II) systems, they have a relatively short lifetime in acetonitrile. Electrochemical studies reveal that all of the Ru(II) complexes display chemically reversible metal-based oxidations. Re(I) complexes only display irreversible metal-based oxidations. In most cases, the reduction processes were not fully chemically reversible. The electrochemical and optical studies reveal that the nature of the lowest excited state of these complexes--particularly, the systems incorporating dppz--is highly dependent on the nature of the coordinated ligands. Calculations indicate that, although the excited state of most of the complexes is centered on the qtpy or Meqtpy(2+) ligands, the excited state of the complexes containing dppz ligands is switched away from the dppz by qtpy methylation. A crystallographic study on one of the dicationic ruthenium(II) structures reveals that it forms an inclusion complex with benzene.

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Section: Resultssupporting

confidence: 82%

Section: Spectral Studiessupporting

confidence: 87%

Section: Spectral Studiessupporting

confidence: 87%

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Tuning the Excited State of Photoactive Building Blocks for Metal‐Templated Self‐Assembly

Ahmad

Meijer

Thomas

2011

Chemistry An Asian Journal

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“…We tentatively assign these bands to CT transitions from a metal-centered d p orbital to p* orbitals localized on the 4,4'-bipyridinium unit [CT(P-A)]. [34] It seems unlikely that such a CT interaction be through bond because 1) the metal complex and 4,4'-bipyridinium moieties are electronically insulated by two methylene groups, and 2) the far red and infrared absorption bands are not observed for the rotaxane complexes. The inspection of physical CPK models suggests that folded conformations in which the A unit is close to the P unit can indeed exist for 6 5 + , but not for the rotaxane complexes 7 5 + -9 5 + , owing to the presence of the macrocycle, which enforces the anti conformation of the central NCH 2 CH 2 N ethane fragment.…”

Section: Resultsmentioning

confidence: 99%

Wire‐Type Ruthenium(II) Complexes with Terpyridine‐Containing [2]Rotaxanes as Ligands: Synthesis, Characterization, and Photophysical Properties

Davidson

Loeb

Passaniti

et al. 2006

Chemistry A European J

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[2]Rotaxanes based on the 1,2-bis(pyridinium)ethane subset[24]crown-8 ether motif were prepared that contain a terminal terpyridine group for coordination to a transition-metal ion. These rotaxane ligands were utilized in the preparation of a series of heteroleptic [Ru(terpy)(terpy-rotaxane)]2+ complexes. The compounds were characterized by 1D and 2D 1H NMR spectroscopy, X-ray crystallography, and high-resolution electrospray ionization mass spectrometry. The effect of using a rotaxane as a ligand was probed by UV/Vis/NIR absorption and emission spectroscopy of the Ru(II) complexes. In contrast with the parent [Ru(terpy)(2)]2+ complex, at room temperature the examined complexes exhibit a luminescence band in the near infrared region and a relatively long lived triplet metal-to-ligand charge-transfer (3MLCT) excited state, owing to the presence of strong-electron-acceptor pyridinium substituents on one of the two terpy ligands. Visible-light excitation of the Ru-based chromophore in acetonitrile at room temperature causes an electron transfer to the covalently linked 4,4'-bipyridinium unit and the quenching of the MLCT luminescence. The 3MLCT excited state, however, is not quenched at all in rigid matrix at 77 K. The rotaxane structure was found to affect the absorption and luminescence properties of the complexes. In particular, when a crown ether surrounds the cationic axle, the photoinduced electron-transfer process is slowed down by a factor from 2 to 3. Such features, together with the synthetic and structural advantages offered by [Ru(terpy)2]2+-type complexes compared to, for example, [Ru(bpy)3]2+-type compounds, render these rotaxane-metal complexes promising candidates for the construction of photochemical molecular devices with a wire-type structure.

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“…The photophysical behavior of transition metal complexes contains numerous examples of complexes which exhibit luminescence from metal-to-ligand charge transfer (MLCT) excited states − and complexes which also exhibit emission from excited states that can formally be described as ligand localized states . Far fewer examples exist of complexes having two coexisting spectroscopically observable excited states. 3c,− Some metalloporphyrins exhibit phosphorescence and delayed fluorescence resulting from intersystem crossing from the triplet back to the higher energy singlet excited state .…”

Section: Introductionmentioning

confidence: 99%

Coexistence of Ligand Localized and MLCT Excited States in a 2-(2‘-Pyridyl)benzo[g]quinoline Complex of Ruthenium(II)

et al. 1996

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The photophysical behavior of complexes of the type [(bpy) 2 Ru(L)](PF 6 ) 2 , where L is a 2-(2′-pyridyl)quinoline or 2-(2′-pyridyl)benzo[g]quinoline derivative, was investigated in acetonitrile solutions and ethanol-methanol glasses. The luminescence from each complex originates from a metal-to-ligand charge transfer excited state and the energy of the emission maxima correlate with other reported quinoline complexes of Ru(II). The 2-(2′-pyridyl)benzo[g]quinoline complex has a unique transient absorption spectrum with a decay rate constant approximately 30 times less than the luminescence decay rate constant, indicating the existence of two nonequilibrated excited states in the complex. Comparison with other related complexes suggests the long-lived transient absorption may be due to a ligand localized (π f π*) excited state. The pyridylquinoline complex exhibits behavior characteristic of a single MLCT excited state.

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Multiple emissions from charge transfer excited states of ruthenium(II)—polypyridine complexes

Cited by 47 publications

References 29 publications

Tuning the Excited State of Photoactive Building Blocks for Metal‐Templated Self‐Assembly

Tuning the Excited State of Photoactive Building Blocks for Metal‐Templated Self‐Assembly

Wire‐Type Ruthenium(II) Complexes with Terpyridine‐Containing [2]Rotaxanes as Ligands: Synthesis, Characterization, and Photophysical Properties

Coexistence of Ligand Localized and MLCT Excited States in a 2-(2‘-Pyridyl)benzo[g]quinoline Complex of Ruthenium(II)

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