Nonradiative decay in rhenium(I) monometallic complexes of 2,3-di-2-pyridylpyrazine

Baiano, John A.; Murphy, W. Rorer

doi:10.1021/ic00024a027

Cited by 25 publications

(12 citation statements)

References 3 publications

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“…As expected from previous studies, [6][7][8][9][10]16] the spectra of the rhenium(I) complexes are much simpler than that of their ruthenium(II) analogs, consisting of intense absorption bands around 240 to 330 nm-assigned to ligand-centered p!p* transitions characteristic of aromatic nitrogen donor ligands-and 1 MLCT transition absorptions centered between 375 and 460 nm. Unlike their Ru II analogs 13 and 14, which contain pyridinium units, the Re I complexes display no well-defined low energy bands.…”

Section: Spectral Studiessupporting

confidence: 76%

“…[6] Studies show that this group of complexes are also able to luminesce from the triplet MLCT state with lifetimes ranging between 100 ns and 100 ms in a room temperature solution. [6][7][8][9][10] A second field that has rapidly emerged in the last two decades is the metal templated self-assembly of metallomacrocycles and other related molecular architectures. [11] Much of this work has exploited classically labile metal centers, such as Pd II , Cu I , and Co II , to produce thermodynamically favored equilibrium products.…”

Section: Introductionmentioning

confidence: 99%

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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: Spectral Studiessupporting

confidence: 76%

Section: Introductionmentioning

confidence: 99%

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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“…In photochemical and photophysical studies of polypyridyl complexes, mixed chelates and unsymmetrical polypyridyl ligands are frequently used to fine-tune excited-state properties and build molecular assemblies. − As the symmetry of these complexes is lowered, a number of important questions arise concerning electronic structure in the lowest-lying metal-to-ligand charge transfer (MLCT) excited states: (1) In multiple chelates, which ligand is the ultimate acceptor? (2) In complexes with two or more identical acceptor ligands, is the excited electron localized on one ligand or is it delocalized over both?…”

Section: Introductionmentioning

confidence: 78%

Excited-State Electronic Structure in Polypyridyl Complexes Containing Unsymmetrical Ligands

et al. 1999

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Step-scan Fourier transform infrared absorption difference time-resolved (S(2)FTIR DeltaA TRS) and time-resolved resonance Raman (TR(3)) spectroscopies have been applied to a series of questions related to excited-state structure in the metal-to-ligand charge transfer (MLCT) excited states of [Ru(bpy)(2)(4,4'-(CO(2)Et)(2)bpy)](2+), [Ru(bpy)(2)(4-CO(2)Et-4'-CH(3)bpy)](2+), [Ru(bpy)(4,4'-(CO(2)Et)(2)bpy)(2)](2+), [Ru(4,4'-(CO(2)Et)(2)bpy)(3)](2+), [Ru(bpy)(2)(4,4'-(CONEt(2))(2)bpy)](2+), [Ru(bpy)(2)(4-CONEt(2)-4'-CH(3)bpy)](2+), and [Ru(4-CONEt(2)-4'-CH(3)bpy)(3)](2+) (bpy is 2,2'-bipyridine). These complexes contain bpy ligands which are either symmetrically or unsymmetrically derivatized with electron-withdrawing ester or amide substituents. Analysis of the vibrational data, largely based on the magnitudes of the nu(CO) shifts of the amide and ester substituents (Deltanu(CO)), reveals that the ester- or amide-derivatized ligands are the ultimate acceptors and that the excited electron is localized on one acceptor ligand on the nanosecond time scale. In the unsymmetrically substituted acceptor ligands, the excited electron is largely polarized toward the ester- or amide-derivatized pyridine rings. In the MLCT excited states of [Ru(bpy)(2)(4,4'-(CO(2)Et)(2)bpy)](2+) and [Ru(bpy)(2)(4,4'-(CONEt(2))(2)bpy)](2+), Deltanu(CO) is only 60-70% of that observed upon complete ligand reduction due to a strong polarization interaction in the excited state between the dpi(5) Ru(III) core and the excited electron.

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“…As a consequence, γ remained constant (eq 5), and ℏω M as well as the vibronically induced electronic coupling was essentially invariant. 14,53,84,86,87 T pp and D p did not show any correlation with the other complexes. Franck−Condon line-shape analysis of the photoluminescence spectra at 77 K revealed that both T pp and D p possessed significantly more delocalized excited states than the related dinuclear and trinuclear complexes, as was underlined by their low Huang−Rhys factors (S M ).…”

Section: ■ Results and Discussionmentioning

confidence: 76%

“…This agreed well with previous studies of a series of Ru(II) and Os(II) complexes, where the energy gap was varied by changing the non-chromophoric ligand (not implicated in the emission process). 14,53,58,84,87 In this study, the chromophoric ligand was instead varied and such a correlation was therefore interesting, as it suggested that, for the four complexes, the Huang−Rhys factor (S M ) decreased linearly with the energy gap. As a consequence, γ remained constant (eq 5), and ℏω M as well as the vibronically induced electronic coupling was essentially invariant.…”

Section: ■ Results and Discussionmentioning

confidence: 95%

MLCT Excited-State Behavior of Trinuclear Ruthenium(II) 2,2′-Bipyridine Complexes

et al. 2020

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Four trinuclear ruthenium(II) polypyridyl complexes were synthesized, and a detailed investigation of their excited-state properties was performed. The tritopic sexi-pyridine bridging ligands were obtained via para or meta substitution of a central 2,2′-bipyridine fragment. A para connection between the 2,2′-bipyridine chelating moieties of the bridging ligand led to a red-shifted MLCT absorption band in the visible part of the spectra, whereas the meta connection induced a broadening of the LC transitions in the UV region. A convergent energy transfer from the two peripheral metal centers to the central Ru(II) moiety was observed for all trinuclear complexes. These complexes were in thermal equilibrium with an upper-lying 3 MLCT excited state over the investigated range of temperatures. For all complexes, deactivation via the 3 MC excited state was absent at room temperature. Importantly, the connection in the para position for both central and peripheral 2,2′-bipyridines of the bridging ligand resulted in a trinuclear complex (T pp ) that absorbed more visible light, had a longer-lived excited state, and had a higher photoluminescence quantum yield than the parent [Ru(bpy) 3 ] 2+ , despite its redshifted photoluminescence. This behavior was attributed to the presence of a highly delocalized excited state for T pp .

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Nonradiative decay in rhenium(I) monometallic complexes of 2,3-di-2-pyridylpyrazine

Cited by 25 publications

References 3 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

Excited-State Electronic Structure in Polypyridyl Complexes Containing Unsymmetrical Ligands

MLCT Excited-State Behavior of Trinuclear Ruthenium(II) 2,2′-Bipyridine Complexes

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