Interligand Electron Transfer Dynamics in Os<sup>II</sup>(bpy)<sub>3</sub>:  Experimental Results and Model Calculations

Cushing, J. P.; Butoi, Carmen I.; Kelley, David F.

doi:10.1021/jp970587c

Cited by 31 publications

(37 citation statements)

References 41 publications

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“…Earlier transient absorption experiments probed an intense ESA resonance localized to the bipyridine ligands at wavelengths near 370 nm. [32][33][34] The polarization dependence of the ESA transition detected at visible wavelengths is quite similar to the resonance detected in the UV. Signals measured with ZZZZ and ZZXX polarization conditions respectively possess subpicosecond rising and decaying components particularly evident at the pump wavelengths of 680 and 645 nm.…”

Section: Resultssupporting

confidence: 65%

Nonlinear Optical Detection of Electron Transfer Adiabaticity in Metal Polypyridyl Complexes

Miller

Moran

2010

J. Phys. Chem. A

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Nonlinear optical signatures of electron transfer (ET) adiabaticity are investigated in a prototypical metal polypyridyl system, Os(II)(bpy)(3), known to possess large interligand couplings. Together with a theoretical model, transient absorption anisotropy (TAA) experiments show that field-matter interactions occur with diabatic basis states despite these large couplings. In addition, activated and activationless interligand ET mechanisms are distinguished with a series of TAA experiments in which the pump pulse frequency is tuned over a wide range. At lower pump frequencies, activated interligand ET, which occurs with a time constant of approximately 600 fs, is the dominant mechanism. However, an activationless mechanism becomes most prominent when the pump pulse is tuned by only 800 cm(-1) to higher frequency. This sensitivity of the ET mechanism to the pump frequency agrees with earlier experimental work that estimated an activation energy barrier of 875 cm(-1). The premise of signal interpretation in this paper is that the basis states appropriate for modeling nonradiative relaxation also govern the optical response. Model calculations suggest that optical nonlinearities corresponding to diabatic and adiabatic bases are readily distinguished with TAA experiments. In the diabatic basis, field-matter interaction sequences are restricted to terms in which the pump and probe pulses interact with the same transition dipoles, whereas the adiabatic basis imposes no such restriction and supports a class of coherent cross terms in the nonlinear response function. It is suggested that TAA should be preferred to alternative methods of studying ET adiabaticity that vary solvents and/or temperature. Altering the solvent, for example, generally also impacts solvent reorganization energies and the free energies of the donor and acceptor states. Parallels are discussed between the present work and research aimed at understanding energy transfer mechanisms in molecular aggregates.

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Section: Resultssupporting

confidence: 65%

Nonlinear Optical Detection of Electron Transfer Adiabaticity in Metal Polypyridyl Complexes

Miller

Moran

2010

J. Phys. Chem. A

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“…The ILET process in Ru(II) and Os(II) tris-polypyridyl complexes has been the topic of much previous research. ,− The current consensus, based on both experimental , and computational , results, suggests that ILET occurs on a subpicosecond time scale in both [Ru(bpy) 3 ] 2+ and [Os(bpy) 3 ] 2+ . Moreover, the computational results paint a rich picture, where the electron can be seen to flow, with processes of delocalizing over more than one ligand and relocalizing on a single ligand occurring on an ultrafast time scale.…”

Section: Resultsmentioning

confidence: 99%

Dynamics of the ³MLCT in Ru(II) Terpyridyl Complexes Probed by Ultrafast Spectroscopy: Evidence of Excited-State Equilibration and Interligand Electron Transfer

2012

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Ground- and excited-state properties of [Ru(tpy)(2)](2+), [Ru(tpy)(ttpy)](2+), and [Ru(ttpy)(2)](2+) (where tpy = 2,2':6',2″-terpyridine and ttpy = 4'-(4-methylphenyl)-2,2':6',2″-terpyridine) in room temperature acetonitrile have been investigated using linear absorption, electrochemical, and ultrafast transient pump-probe techniques. Spectroelectrochemistry was used to assign features observed in the transient spectra while single wavelength kinetics collected at a variety of probe wavelengths were used to monitor temporal evolution of the MLCT excited state. From these data, the excited-state lifetime of each complex was recovered and the rate limiting decay step was identified. In the bis-heteroleptic complex [Ru(tpy)(ttpy)](2+), photoexcitation to the (1)MLCT manifold generates both tpy-localized and ttpy-localized excited states. Accordingly, interligand electron transfer (ILET) from tpy-localized to the ttpy-localized (3)MLCT excited states is observable and the time scale has been measured to be 3 ps. For the homoleptic complex [Ru(tpy)(2)](2+), evidence for equilibration of the (3)MLCT excited-state population with the (3)MC has been observed and the time scale is reported at 2 ps.

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“…If ILET occurs on the same time scale as electron injection, then ILET reduces the quantum yield for electron injection and diminishes the amplitude of the fast component. The rates of ILET have been studied in the symmetric compounds Ru II (bipyridine) 3 and Os II (bipyridine) 3 . − In these cases ILET times of tens of picoseconds were observed, which are much faster that the hundreds of picoseconds time scale required here for ILET to compete with electron injection. However, the reorganization energy for ILET is quite small, and if there is a considerable difference in the attached and nonattached ligand π* energies, then ILET will be in the inverted region and slower rates would be expected.…”

Section: Resultsmentioning

confidence: 99%

Electron Injection Dynamics of Ru^II(4,4‘-dicarboxy-2,2‘-bipyridine)₂cis(NCS)₂ Adsorbed on MoS₂ Nanoclusters

et al. 1999

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The electron injection dynamics of Ru II (4,4′-dicarboxy-2,2′-bipyridine) 2 cis(NCS) 2 (N3 dye) adsorbed on MoS 2 nanoclusters have been studied using static and time-resolved optical spectroscopy. Static spectroscopy and the comparison with Ru II (2,2′-bipyridine) 2 cis(NCS) 2 indicate that the N3 is bound to the MoS 2 nanoclusters and that the binding occurs through the carboxylates. The static absorption spectrum of adsorbed N3/MoS 2 is red shifted about 1.2 nm compared to N3 in an equivalent acetonitrile/hexanol/tridodecylmethylammonium iodide solution. The extent of the spectral shift indicates that the coupling is comparable to that in the N3/ TiO 2 case. The time-resolved results indicate that about 35% of the adsorbed dyes inject electrons into the MoS 2 conduction band on the 250 ps time scale, and about 65% do not inject. These results indicate that electron injection is comparatively slow in these systems (250 ps compared to <100 fs in N3/TiO 2 ) because of the low density of conduction band states in these quantum-confined nanoclusters. We speculate that the biphasic decay may be understood in terms of a mechanism in which one of the 4,4′-dicarboxy-2,2′-bipyridine ligands is attached to the nanocluster, while the other ligand is not attached. The attached and nonattached ligands have strong and very weak electronic coupling to the nanocluster, respectively. Electrons in the MLCT state localized on the attached ligand undergo injection on the 250 ps time scale, while those localized on the nonattached ligand do not inject. In this model, attached-to-nonattached interligand electron transfer competes with electron injection and lowers the injection quantum yield to the observed value of 35%.

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Interligand Electron Transfer Dynamics in Os^II(bpy)₃: Experimental Results and Model Calculations

Cited by 31 publications

References 41 publications

Nonlinear Optical Detection of Electron Transfer Adiabaticity in Metal Polypyridyl Complexes

Nonlinear Optical Detection of Electron Transfer Adiabaticity in Metal Polypyridyl Complexes

Dynamics of the ³MLCT in Ru(II) Terpyridyl Complexes Probed by Ultrafast Spectroscopy: Evidence of Excited-State Equilibration and Interligand Electron Transfer

Electron Injection Dynamics of Ru^II(4,4‘-dicarboxy-2,2‘-bipyridine)₂cis(NCS)₂ Adsorbed on MoS₂ Nanoclusters

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Interligand Electron Transfer Dynamics in OsII(bpy)3: Experimental Results and Model Calculations

Cited by 31 publications

References 41 publications

Nonlinear Optical Detection of Electron Transfer Adiabaticity in Metal Polypyridyl Complexes

Nonlinear Optical Detection of Electron Transfer Adiabaticity in Metal Polypyridyl Complexes

Dynamics of the 3MLCT in Ru(II) Terpyridyl Complexes Probed by Ultrafast Spectroscopy: Evidence of Excited-State Equilibration and Interligand Electron Transfer

Electron Injection Dynamics of RuII(4,4‘-dicarboxy-2,2‘-bipyridine)2cis(NCS)2 Adsorbed on MoS2 Nanoclusters

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Interligand Electron Transfer Dynamics in Os^II(bpy)₃: Experimental Results and Model Calculations

Dynamics of the ³MLCT in Ru(II) Terpyridyl Complexes Probed by Ultrafast Spectroscopy: Evidence of Excited-State Equilibration and Interligand Electron Transfer

Electron Injection Dynamics of Ru^II(4,4‘-dicarboxy-2,2‘-bipyridine)₂cis(NCS)₂ Adsorbed on MoS₂ Nanoclusters