Time-Resolved Absorption, Infrared, and Resonance Raman Spectra of the Complexes [Ru(X)(R)(CO)2(.alpha.-Diimine)] (X = Halide; R = Alkyl): Influence of X on the Charge Transfer Character of the Lowest Excited State

Nieuwenhuis, Heleen A.; Stufkens, Derk J.; McNicholl, R.-A.; Al-Obaidi, Ala H. R.; Coates, Colin G.; Bell, Steven E. J.; McGarvey, John J.; Westwell, Jeremy R.; George, Michael W.; Turner, James J.

doi:10.1021/ja00125a020

Cited by 57 publications

(39 citation statements)

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“…20, 21 The majority of TRIR studies on the excited state nature of inorganic chromophores have focussed on d 6 and d 8 metal complexes, e.g. Re(), Ru(), Os() and Pt(), possessing MLCT, 20,22 mixed MLCT/halogento-ligand CT (XLCT), 23 σ-π*, 24 and π-π* 22,25 excited states. Vlcek and co-workers have used 26 ps-TRIR to monitor the excited states and photochemistry of [Cr(2,2Ј-bipy 27 Excitation of a metal complex to produce a MLCT excited state results in a reduction of electron density at the metal centre and, in the case of metal carbonyl complexes, a shift of the ν(CO) bands to higher energy by ca.…”

Section: Applications Of Trir 1 Probing Excited States With Trirmentioning

confidence: 99%

Using picosecond and nanosecond time-resolved infrared spectroscopy for the investigation of excited states and reaction intermediates of inorganic systemsBased on the presentation given at Dalton Discussion No. 6, 9?11th September 2003, University of York, UK.

et al. 2003

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Time-resolved infrared (TRIR) spectroscopy, a combination of UV flash photolysis and fast infrared detection, is a powerful technique for probing excited states and detecting reaction intermediates. In this Perspective we highlight the application of TRIR to excited states by probing the nature of the lowest excited states of fac-[Re(CO) 3 (dppz-Cl 2 )(R)] n؉ (R ‫؍‬ Cl ؊ (n ‫؍‬ 0), py (n ‫؍‬ 1) and 4-Me 2 N-py (n ‫؍‬ 1); dppz-Cl 2 ‫؍‬ 11,12-dichlorodipyrido-[3,2-a:2Ј,3Ј-c]phenazine) in CH 3 CN. The characterisation of [Cr( 6 -C 6 H 6 )(CO) 2 Xe] and [Re( 5 -C 5 H 5 )(CO) 2 (C 2 H 6 )] in supercritical Xe and liquid ethane solution exemplifies how this technique can be applied to detect new organometallic species.

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Section: Applications Of Trir 1 Probing Excited States With Trirmentioning

confidence: 99%

Using picosecond and nanosecond time-resolved infrared spectroscopy for the investigation of excited states and reaction intermediates of inorganic systemsBased on the presentation given at Dalton Discussion No. 6, 9?11th September 2003, University of York, UK.

et al. 2003

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“…The sample absorbance at the excitation wavelength was kept between 0.3 and 0.5. The time-resolved infrared (TRIR) spectra were collected with a system described elsewhere [30,55]. The 532 nm (fwhm = 10 ns) line of a Nd:YAG laser was used to excite the sample.…”

Section: Mmentioning

confidence: 99%

Mechanism of an Alkyl‐Dependent Photochemical Homolysis of the Re–Alkyl Bond in [Re(R)(CO)₃(α‐diimine)] Complexes via a Reactive σπ^* Excited State

Rossenaar

Kleverlaan

Ven

et al. 1996

Chemistry A European J

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MLCT excitation of the complexes [Re(R)(CO),(a-diimine)] (R = Me, Et, benzyl (Bz); a-diimine = iPr-PyCa, R-DAB) results in the homolysis of the Re-R bond leading to the formation of radicals R and [Re(CO),(a-diimine)]' as primary photoproducts. The quantum yield of this photoprocess is dependent on the alkyl group used. For R = Me, the quantum yield is low and depends on the temperature and excitation wavelength, whereas for R = Et and Bz the quantum yield is near unity and independent of T and A,,,. The reaction is shown to proceed via a o(Re-R)x* excited state that is rapidly (< 20 ps) populated by a nonradiative transition from the optically excited MLCT state. Time-resolved IR and UV/Vis absorption spectra studied in the ns-ps and ps-ps time domains, respectively, show that the ox* excited state is rather long-lived (z x 250 ns) in noncoordinating solvents; the dissociation of the Re-R bond from this state is strongly accelerated by polar or coordinating solvents (rent < 20 ps). The ox* excited state is spectroscopically characterized by a (presumably ox* -+ MLCT) transition at approximately 500 nm and by CO stretching frequencies closely resembling their ground-state values. The relative energies of the MLCT and reactive cm* states, controlled by the nature of the alkyl ligand, determine the photoreactivity of the complexes.

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“…1) and [Ru(E)(R)(CO) 2 (a-diimine)] (II) complexes, where R = alkyl or benzyl, E = I or SnPh3, and a-diimine = 4,4'-dimethyl-2,2'-bipyridine (DMB) or N,N'-diisopropyl-1,4-diazabutadiene (iPr-DAB) have been subject of detailed spectroscopic (UVNis, IR, Raman, NMR, EPR) studies [1][2][3][4][5][6][7]. It has been shown that photoexcitation of these complexes can trigger homolysis of the metal-alkyl (benzyl) bond.…”

Section: Introductionmentioning

confidence: 99%

“…It appears, therefore, that excitation to the 'MLCT state of [Re(CH 3 ) (CO)3(DMB)] is followed by two independent deactivation pathways, one producing a nonreactive 3 MLCT state and another giving a short-lived excited state from which bond dissociation occurs [7]. Spectroscopic and theoretical studies indicate that bond dissociation requires that photoexcitation populates a state with a(metal-alkyl)ic'(a-diimine) character [1][2][3][4][5][6][7]. According to this interpretation, variations in photoreactivity stems from changes in the quantum yield of formation of reactive ait excited states.…”

Section: Introductionmentioning

confidence: 99%

FT-EPR study of alkyl radicals formed in the photochemical reaction of Re(alkyl)(α-diimine) and Ru(alkyl)(α-diimine) complexes

et al. 1998

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A Fourier transform EPR (FT-EPR) study was made of the photochemistry of [Re(R)(CO) 3 (a-diimine)] and [Ru(E)(R)(CO) 2 (a-diimine)] complexes, where R = alkyl or benzyl, E = I or SnPh 3 , and a-diimine = 4,4'-dimethyl-2,2'-bipyridine (DMB) or N,N'-diisopropyl-1,4-diazabutadiene (iPr-DAB). Photoexcitation of these complexes leads to homolysis of the metal-alkyl (benzyl) bonds as evident from the detection of the spectra of the alkyl (benzyl) radicals. FT-EPR spectra display strong spin polarization effects attributed to Triplet Mechanism (TM) and Radical Pair Mechanism (RPM) Chemically Induced Dynamic Electron Polarization (CIDEP). CIDEP patterns point to bond dissociation via a triplet state precursor. For a number of complexes, spin polarization was found to exhibit unusually large solvent effects, whereas for one complex the CIDEP pattern proved to be sensitive to the wavelength of laser light used to initiate bond dissociation. These effects reflect the strong dependence of CIDEP on the character of the excited states involved in the photochemical reactions and contribute to the understanding of the reaction mechanism.

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Time-Resolved Absorption, Infrared, and Resonance Raman Spectra of the Complexes [Ru(X)(R)(CO)2(.alpha.-Diimine)] (X = Halide; R = Alkyl): Influence of X on the Charge Transfer Character of the Lowest Excited State

Cited by 57 publications

References 8 publications

Using picosecond and nanosecond time-resolved infrared spectroscopy for the investigation of excited states and reaction intermediates of inorganic systemsBased on the presentation given at Dalton Discussion No. 6, 9?11th September 2003, University of York, UK.

Using picosecond and nanosecond time-resolved infrared spectroscopy for the investigation of excited states and reaction intermediates of inorganic systemsBased on the presentation given at Dalton Discussion No. 6, 9?11th September 2003, University of York, UK.

Mechanism of an Alkyl‐Dependent Photochemical Homolysis of the Re–Alkyl Bond in [Re(R)(CO)₃(α‐diimine)] Complexes via a Reactive σπ^* Excited State

FT-EPR study of alkyl radicals formed in the photochemical reaction of Re(alkyl)(α-diimine) and Ru(alkyl)(α-diimine) complexes

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Time-Resolved Absorption, Infrared, and Resonance Raman Spectra of the Complexes [Ru(X)(R)(CO)2(.alpha.-Diimine)] (X = Halide; R = Alkyl): Influence of X on the Charge Transfer Character of the Lowest Excited State

Cited by 57 publications

References 8 publications

Using picosecond and nanosecond time-resolved infrared spectroscopy for the investigation of excited states and reaction intermediates of inorganic systemsBased on the presentation given at Dalton Discussion No. 6, 9?11th September 2003, University of York, UK.

Using picosecond and nanosecond time-resolved infrared spectroscopy for the investigation of excited states and reaction intermediates of inorganic systemsBased on the presentation given at Dalton Discussion No. 6, 9?11th September 2003, University of York, UK.

Mechanism of an Alkyl‐Dependent Photochemical Homolysis of the Re–Alkyl Bond in [Re(R)(CO)3(α‐diimine)] Complexes via a Reactive σπ* Excited State

FT-EPR study of alkyl radicals formed in the photochemical reaction of Re(alkyl)(α-diimine) and Ru(alkyl)(α-diimine) complexes

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Mechanism of an Alkyl‐Dependent Photochemical Homolysis of the Re–Alkyl Bond in [Re(R)(CO)₃(α‐diimine)] Complexes via a Reactive σπ^* Excited State