Electronic Distribution in the Metal-to-Ligand Charge Transfer (MLCT) Excited States of [(4,4‘-(X)2bpy)(CO)3ReI(4,4‘-bpy)ReI(CO)3(4,4‘-(X)2bpy)]2+(X = H, CH3). Application of Time-Resolved Infrared and Resonance Raman Spectroscopies

Omberg, Kristin M.; Schoonover, Jon R.; Meyer, Thomas J.

doi:10.1021/jp972522f

Cited by 24 publications

(19 citation statements)

References 58 publications

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“…The three ν(CO) bands in the ground state are shifted by only −6, −3, and −15 cm -1 , to 2034, 1935, and 1917 cm -1 . Ground-to-excited state shifts for MLCT excited states are typically much larger and in the opposite direction (for fac- [Re II (bpy •- )(CO) 3 (4-Etpy)] + , the shifts are +25, +80, and +35 cm -1 in CH 3 CN at 298 K) . The small shifts in the photochemical transient show that the electron density at the metal is relatively unperturbed compared to the ground state. − …”

Section: Discussionmentioning

confidence: 99%

“…Time-Resolved Infrared. Time-resolved infrared measurements utilized a BioRad FTS 60A/896 step-scan interferometer with an external MCT detector as previously described. , A recent upgrade of this instrument utilizes fast data processing techniques. In this arrangement, the IR signal from the detector was amplified and processed by a BioRad Fast TRS board installed in a Pentium PC.…”

Section: Methodsmentioning

confidence: 99%

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Excited-State Electron Transfer in a Chromophore−Quencher Complex. Spectroscopic Identification of a Redox-Separated State

López¹,

Leiva²,

Zuloaga³

et al. 1999

Inorg. Chem.

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In the chromophore-quencher complex fac-[Re(Aqphen)(CO)(3)(py-PTZ)](+) (Aqphen is 12,17-dihydronaphtho[2,3-h]dipyrido[3,2-a:2',3'-c]-phenazine-12,17-dione; py-PTZ is 10-(4-picolyl)phenothiazine), Aqphen is a dppz derivative, containing a pendant quinone acceptor at the terminus of a rigid ligand framework. This introduces a third, low-lying, ligand-based pi acceptor level localized largely on the quinone fragment. Laser flash excitation of fac-[Re(Aqphen)(CO)(3)(py-PTZ)](+) (354.7 nm; in 1,2-dichloroethane) results in the appearance of a relatively long-lived transient that decays with tau(298K) = 300 ns (k = 3.3 x 10(6) s(-)(1)). Application of transient absorption, time-resolved resonance Raman, and time-resolved infrared spectroscopies proves that this transient is the redox-separated state fac-[Re(I)(Aqphen(*)(-)())(CO)(3)(py-PTZ(*)(+)())](+) in which the excited electron is localized largely on the quinone portion of the Aqphen ligand.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Excited-State Electron Transfer in a Chromophore−Quencher Complex. Spectroscopic Identification of a Redox-Separated State

López¹,

Leiva²,

Zuloaga³

et al. 1999

Inorg. Chem.

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“…Nanosecond transient absorption spectra were obtained on previously described instrumentation, with the third harmonic of a Nd:YAG laser (355 nm, 10 ns fwhm, 5 mJ pulse -1 ) as the excitation source. Time-resolved infrared spectroscopy was carried out on a step-scan FTIR instrument that has been previously described. , Samples were dissolved in CH 3 CN and were purged with Ar. Excitation was effected using the third harmonic output of a Nd:YAG laser (355 nm).…”

Section: Methodsmentioning

confidence: 99%

“…Time-resolved infrared spectroscopy was carried out on a step-scan FTIR instrument that has been previously described. 30,31 with Ar. Excitation was effected using the third harmonic output of a Nd:YAG laser (355 nm).…”

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confidence: 99%

Excited-State Structure and Delocalization in Ruthenium(II)−Bipyridine Complexes That Contain Phenyleneethynylene Substituents

et al. 2001

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A comprehensive photophysical study has been carried out on the two complexes [(bpy) 2 Ru(4,4′-PE-bpy)] 2+ and [(bpy) 2 Ru(5,5′-PE-bpy)] 2+ (44Ru and 55Ru, respectively, where bpy ) 2,2′-bipyridine and PE ) phenyleneethynylene). The objective of this work is to determine the effect of the phenyleneethynylene substituents on the properties of the metal-to-ligand charge-transfer excited state. The complexes have been characterized by using UV-visible absorption, photoluminescence, and UV-visible and infrared transient absorption spectroscopy. The results indicate that the MLCT excited state is localized on the PE-substituted bpy ligands. Moreover, the photophysical data indicate that in the MLCT excited state the excited electron is delocalized into the PE substituents and the manifestations of the electronic delocalization are larger when the substituents are in the 4,4′-positions.

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“…An alternate method is the two-color experiment in which the pump pulse creates the transient species and resonance Raman scattering is produced by the probe pulsethe delay between the arrival of each of these pulses at the sample may be used to give temporal resolution . In the case of MLCT excited states the key spectral signatures that manifest in the resonance Raman spectra are often features of the ligand radical anion species. ,,− For example Woodruff et al, in their seminal work on the resonance Raman excited-state spectrum of [Ru(bpy) 3 ] 2+ , were able to show the presence of bpy •- in the MLCT state by comparing the complexes excited-state spectrum with that of chemically generated bpy •- . The close correspondence between features in these two spectra provided strong evidence for [Ru (III) (bpy) 2 (bpy •- )] 2+ * formulation of the MLCT excited state.…”

Section: Introductionmentioning

confidence: 99%

Probing the Excited States of Ru(II) Complexes with Dipyrido[2,3-a:3‘,2‘-c]phenazine: A Transient Resonance Raman Spectroscopy and Computational Study

2005

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The lifetimes and transient resonance Raman spectra for Ru(II) complexes with the dipyrido[2,3-a:3',2'-c]phenazine (ppb) ligand and substituted analogues have been measured. The effect of altering the Ru(II) center ([Ru(CN)4]2- versus [Ru(bpy)2]2+), of the complex, on the excited-state lifetimes and spectra has been considered. For [Ru(bpy)2L]2+ complexes the excited-state lifetimes range from 124 to 600 ns in MeCN depending on the substituents on the ppb ligand. For the [Ru(CN)4L]2- complexes the lifetimes in H2O are approximately 5 ns. The transient resonance Raman spectra for the MLCT excited states of these complexes have been measured. The data are analyzed by comparison with the resonance Raman spectra of the electrochemically reduced [(PPh3)2Cu(mu-L*-)Cu(PPh3)2]+ complexes. The vibrational spectra of the complexes have been modeled using DFT methods. For experimental ground-state vibrational spectra of the complexes the data may be compared to calculated spectra of the ligand or metal complex. It is found that the mean absolute deviation between experimental and calculated frequencies is less for the calculation on the respective metal complexes than for the ligand. For the transient resonance Raman spectra of the complexes the observed vibrational bands may be compared with those of the calculated ligand radical anion, the reduced complex [Ru(CN)4L*-]3-, or the triplet state of the complex. In terms of a correlation with the observed transient RR spectra, calculations on the metal complex models offered no significant improvement compared to those based on the ligand radical anion alone. In all cases small structural changes are predicted on going from the ground to excited state.

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Electronic Distribution in the Metal-to-Ligand Charge Transfer (MLCT) Excited States of [(4,4‘-(X)₂bpy)(CO)₃Re^I(4,4‘-bpy)Re^I(CO)₃(4,4‘-(X)₂bpy)]²⁺(X = H, CH₃). Application of Time-Resolved Infrared and Resonance Raman Spectroscopies

Cited by 24 publications

References 58 publications

Excited-State Electron Transfer in a Chromophore−Quencher Complex. Spectroscopic Identification of a Redox-Separated State

Excited-State Electron Transfer in a Chromophore−Quencher Complex. Spectroscopic Identification of a Redox-Separated State

Excited-State Structure and Delocalization in Ruthenium(II)−Bipyridine Complexes That Contain Phenyleneethynylene Substituents

Probing the Excited States of Ru(II) Complexes with Dipyrido[2,3-a:3‘,2‘-c]phenazine: A Transient Resonance Raman Spectroscopy and Computational Study

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