The Degree of Charge Transfer in Ground and Charge-Separated States Revealed by Ultrafast Visible Pump/Mid-IR Probe Spectroscopy

Rubtsov, Igor V.; Kang, Youn K.; Redmore, Naomi P.; Allen, Rebecca M.; Zheng, Jieru; Beratan, David N.; Therien, Michael J.

doi:10.1021/ja030674k

Cited by 35 publications

(50 citation statements)

References 11 publications

(16 reference statements)

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“…We believe that the current study illustrates that this method can be extended to inorganic molecules with lowlying 3 IL states bearing appropriate IR-absorbing chromophores. The current results also demonstrate that triplet-state electron density can be directly tracked by TRIR in these chromophores and that frequency red shifts comparable to those observed in charge-transfer imide-bearing systems 7,8 can be realized.…”

supporting

confidence: 65%

Observation of Triplet Intraligand Excited States through Nanosecond Step-Scan Fourier Transform Infrared Spectroscopy

2006

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Nanosecond step-scan Fourier transform infrared spectroscopy permits the observation of triplet intraligand ((3)IL) character in the excited states of [Ru(bpy)2(PNI-phen)]2+ and [Ru(PNI-phen)3]2+ where PNI is 4-piperidinyl-1,8-naphthalimide. After pulsed 355-nm laser excitation, the two ground-state imide C=O bands in each compound are bleached and two substantially lower energy vibrations are produced; the lower energy feature appears as two distinct bands split by an overlapping transient bleach. Model studies confirm that the time-resolved vibrational data are consistent with photoinduced sensitization of the 3IL excited state. Density functional theory calculations also support these assignments because localization of triplet electron density on the PNI moiety is expected to lead to red-shifted C=O vibrations of magnitude similar to those measured experimentally. The current results illustrate that triplet electron density can be directly tracked by time-resolved infrared measurements in metal-organic chromophores and that frequency shifts comparable to those observed in charge-transfer systems can be realized.

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supporting

confidence: 65%

Observation of Triplet Intraligand Excited States through Nanosecond Step-Scan Fourier Transform Infrared Spectroscopy

2006

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“…22). The chargeresonance contribution (C 2 2 ) to G can also be estimated from the electronic coupling matrix element (H DA ) because C 2 = |c 0 c 1 |, which is again |H DA / E| [151].…”

Section: Evaluating 1a-zn Electronic Coupling Utilizing Vis-pump/ir-pmentioning

confidence: 99%

Electron transfer reactions of rigid, cofacially compressed, π-stacked porphyrin–bridge–quinone systems

Kang

Iovine

Therien

2011

Coordination Chemistry Reviews

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“…It is known that electrons and holes in conjugated molecules exhibit intense IR bands, 8,9 especially (C=C) bands, and that their intensities are dependent upon delocalization of charges. 9 Infrared (IR) spectroscopy has previously been used to discern charge transfer states by means of spectral shifts of specific vibrational bands such as (C=O) bands [10][11][12][13][14][15] and (C=C) bands. 16 In a similar 4 manner, we postulate that we can measure the degree of electron localization by spectral shifts of specific vibrational bands.…”

Section: Introductionmentioning

confidence: 99%

Electron Localization of Anions Probed by Nitrile Vibrations

et al. 2015

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Localization and delocalization of electrons is a key concept in chemistry, and is one of the important factors determining the efficiency of electron transport through organic conjugated molecules, which have potential to act as "molecular wires". This, in turn, substantially influences the efficiencies of organic solar cells and other molecular electronic devices. It is also necessary to understand the electronic energy landscape and the dynamics that govern electron transport capabilities in one-dimensional conjugated chains so that we can better define the design principles for conjugated molecules for their applications. We show that nitrile ν(C≡N) vibrations respond to the degree of electron localization in nitrile-substituted organic anions by utilizing time-resolved infrared detection combined with pulse radiolysis. Measurements of a series of aryl nitrile anions allow us to construct a semiempirical calibration curve between the changes in the ν(C≡N) infrared (IR) shifts and the changes in the electronic charges from the neutral to the anion states in the nitriles; more electron localization in the nitrile anion results in larger IR shifts. Furthermore, the IR line width in anions can report a structural change accompanying changes in the electronic density distribution. Probing the shift of the nitrile ν(C≡N) IR vibrational bands enables us to determine how the electron is localized in anions of nitrile-functionalized oligofluorenes, considered as organic mixed-valence compounds. We estimate the diabatic electron transfer distance, electronic coupling strengths, and energy barriers in these mixed-valence compounds. The analysis reveals a dynamic picture, showing that the electron is moving back and forth within the oligomers with a small activation energy of ≤kBT, likely controlled by the movement of dihedral angles between monomer units. Implications for the electron transport capability in molecular wires are discussed.

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The Degree of Charge Transfer in Ground and Charge-Separated States Revealed by Ultrafast Visible Pump/Mid-IR Probe Spectroscopy

Cited by 35 publications

References 11 publications

Observation of Triplet Intraligand Excited States through Nanosecond Step-Scan Fourier Transform Infrared Spectroscopy

Observation of Triplet Intraligand Excited States through Nanosecond Step-Scan Fourier Transform Infrared Spectroscopy

Electron transfer reactions of rigid, cofacially compressed, π-stacked porphyrin–bridge–quinone systems

Electron Localization of Anions Probed by Nitrile Vibrations

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