Mixed valence of a delocalized system: a resonance Raman study of the tetracyanoquinodimethane radical anion

Hoekstra, Ryan M.; Zink, Jeffrey I.; Telo, João P.; Nelsen, Stephen F.

doi:10.1002/poc.1518

Cited by 5 publications

(10 citation statements)

References 52 publications

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“…We have discussed the neighboring orbital model previously . The molecular orbitals involved in the transitions of interest are composed of three groups of atomic orbitals: the nitrogen p z orbital, three oxygen p z orbitals that form three linear combinations of a 2 ″ e″ symmetry, and the single‐node aryl pi orbitals.…”

Section: Resultsmentioning

confidence: 99%

“…We have discussed the neighboring orbital model previously. [4,[44][45][46][47][48][49][50][51][52][53] The molecular orbitals involved in the transitions of interest are composed of three groups of atomic orbitals: the nitrogen p z orbital, three oxygen p z orbitals that form three linear combinations of a 2 00 e 00 symmetry, and the single-node aryl pi orbitals. Each aryl group has two degenerate single node MOs (in addition to the p nodal plane) that are close enough in energy to strongly interact with the nitrogen and oxygen p z orbitals.…”

Section: Neighboring Orbital Model Interpretationmentioning

confidence: 99%

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Excited state mixed valence in a dual‐bridged three‐chromophore system

Dibrelle

Hoekstra

Weaver

et al. 2012

J of Physical Organic Chem

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The optical and resonance Raman spectra of the 2,2′: 6′,2″:6″,6‐trioxytriphenyl‐amine cation are measured and interpreted. This molecule contains two simultaneous types of coupling between three chromophores and two types of bridging atoms. The first and conventional coupling involves a single nitrogen bridge that couples all three aryl groups. The second is provided by the three oxygen atoms, each of which bridges two adjacent aryl groups. There are two bands in the visible region of the optical absorption spectrum; their assignment and the interpretation of the contributing orbitals and electronic states are described in terms of the neighboring orbital model that explains the effects of the two types of coupling. The bonding changes that take place in the excited electronic states are probed by resonance Raman spectroscopy intensities and analyzed using the time‐dependent theory of resonance Raman spectroscopy. The optical absorption spectrum was fit using the measured vibrational frequencies and excited state distortions. The distortions correlate well with the bonding changes predicted by the neighboring orbital model. The resonance Raman data and neighboring orbital model analysis reveal that the two optical absorption bands correspond to charge transfers from aryl groups with different nodal structures in their pi orbitals. Copyright © 2012 John Wiley & Sons, Ltd.

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Section: Resultsmentioning

confidence: 99%

Section: Neighboring Orbital Model Interpretationmentioning

confidence: 99%

Excited state mixed valence in a dual‐bridged three‐chromophore system

Dibrelle

Hoekstra

Weaver

et al. 2012

J of Physical Organic Chem

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“…The enhancement of the MNA bands at 1205 and 1155 cm –1 by 488 nm line suggests that the next electronic transition originates from π–π* excitation in the phenyl ring. According to the time-dependent theory, ,,, the modes of vibrations giving the most intense bands in Raman and RR spectra are responsible for the largest distortions (largest displacements of the excited-state potential surface along their normal coordinates). , The calculated (at 0 K) distances between chosen atoms in the MNA molecule ground and first excited states (in parentheses), differing mostly, are as follows: C–N(O 2 ) 1.447 Ǻ (1.440 Ǻ), C–N(H 2 ) 1.369 Ǻ (1.379 Ǻ), N–O 1.266 Ǻ (1.347 Ǻ), N–O′ 1.265 Ǻ (1.425 Ǻ), and C5–C6 1.380 Ǻ (1.389 Ǻ).…”

Section: Resultsmentioning

confidence: 99%

Helical Superstructure and Charged Polarons Contributions to Optical Nonlinearity of 2-Methyl-4-nitroaniline Crystals Studied by Resonance Raman, Electron Paramagnetic Resonance, Circular Dichroism Spectroscopies, and Quantum Chemical Calculations

et al. 2011

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The Raman excitation profiles of solid 2-methyl-4-nitroaniline (MNA) reveal several band enhancements by intermolecular and intramolecular charge transfer states. Calculated excited- and ground-state molecular geometries and excited state distortions qualitatively determined from Raman spectra indicate multiple vibrations leading to MNA dissociation. Also, overtones and combination tones can generate charged polarons, as detected by electron paramagnetic resonance after the exposure to 980 and 1550 nm laser diodes. The MNA space group Ia (C(s)(4)) is nonchiral; however, the electronic circular dichroism (CD) spectra of solution, KBr pellet, and single crystal were recorded. The crystal chirality is elucidated by room-temperature dynamic disorder, possible helical superstructure along the [102] polar axis, and charged polarons presence. The CD spectra ab initio calculations for MNA neutral and negatively charged monomers, dimers, and trimers, lying along the helix, confirmed the chirality. The role of these findings toward efficient optical nonlinearity and electric conductivity failure is discussed.

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“…1 r 12 ) 1 -erf(ωr 12 ) r 12 + erf(ωr 12 ) r 12 (12) chosen to be 0.30a 0 -1 . This value is based on previous applications where it was shown that this value leads to the best performance for excited-state properties, such as excitation energies.…”

Section: Computational Detailsmentioning

confidence: 99%

Understanding the Resonance Raman Scattering of Donor−Acceptor Complexes using Long-Range Corrected DFT

Silverstein

Jensen

2010

J. Chem. Theory Comput.

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The optical properties involving charge-transfer states of the donor-acceptor electron-transfer complexes carbazole/tetracyanoethylene (carbazole/TCNE) and hexamethylbenzene/tetracyanoethylene (HMB/TCNE) were investigated by utilizing the time-dependent theory of Heller to simulate absorbance and resonance Raman spectra. Excited-state properties were obtained using time-dependent density functional theory (TDDFT) using the global hybrid B3LYP and the long-range corrected LC- ωPBE functionals and compared with experimental results. It is shown that, while reasonable simulations of the absorbance spectra can be made using B3LYP, the resonance Raman spectra for both complexes are poorly described. The LC-ωPBE functional gives a more accurate representation of the excited-state potential energy surfaces in the Franck-Condon region for charge-transfer states, as indicated by the good agreement with the experimental resonance Raman spectrum. For the carbazole/TCNE complex, which includes contributions from two overlapping excited states on its absorbance spectrum, interference effects are discussed, and it is found that detuning from resonance with an excited state results in interference along with other factors. Total vibrational reorganization energy for both complexes is discussed, and it is found that both B3LYP and LC-ωPBE yield reasonable estimates of this quantity compared with experiment.

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Mixed valence of a delocalized system: a resonance Raman study of the tetracyanoquinodimethane radical anion

Cited by 5 publications

References 52 publications

Excited state mixed valence in a dual‐bridged three‐chromophore system

Excited state mixed valence in a dual‐bridged three‐chromophore system

Helical Superstructure and Charged Polarons Contributions to Optical Nonlinearity of 2-Methyl-4-nitroaniline Crystals Studied by Resonance Raman, Electron Paramagnetic Resonance, Circular Dichroism Spectroscopies, and Quantum Chemical Calculations

Understanding the Resonance Raman Scattering of Donor−Acceptor Complexes using Long-Range Corrected DFT

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