Styrene and phenylacetylene: Electronic effects of conjugating substituents “off” and “on” the axis of a benzene ring

Ribblett, Jason W.; Borst, David R.; Pratt, David W.

doi:10.1063/1.480186

Cited by 49 publications

(70 citation statements)

References 32 publications

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“…The orbitals for the syn – anti conformer are very similar. From the perspective of the individual halves of the molecule, calculations predict the S 1 state to be quite similar to the S 1 state of styrene, with HOMO−1→LUMO and HOMO→LUMO+1 being the most important configurations 40. The S 2 state is described by numerous configurations and no simple characterization can be made.…”

Section: Resultsmentioning

confidence: 99%

Pseudo‐Bimolecular [2+2] Cycloaddition Studied by Time‐Resolved Photoelectron Spectroscopy

Brogaard

Boguslavskiy

Schalk

et al. 2011

Chemistry A European J

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The first study of pseudo‐bimolecular cycloaddition reaction dynamics in the gas phase is presented. We used femtosecond time‐resolved photoelectron spectroscopy (TRPES) to study the [2+2] photocycloaddition in the model system pseudo‐gem‐divinyl[2.2]paracyclophane. From X‐ray crystal diffraction measurements we found that the ground‐state molecule can exist in two conformers; a reactive one in which the vinyl groups are immediately situated for [2+2] cycloaddition and a nonreactive conformer in which they point in opposite directions. From the measured S1 lifetimes we assigned a clear relation between the conformation and the excited‐state reactivity; the reactive conformer has a lifetime of 13 ps, populating the ground state through a conical intersection leading to [2+2] cycloaddition, whereas the nonreactive conformer has a lifetime of 400 ps. Ab initio calculations were performed to locate the relevant conical intersection (CI) and calculate an excited‐state [2+2] cycloaddition reaction path. The interpretation of the results is supported by experimental results on the similar but nonreactive pseudo‐para‐divinyl[2.2]paracyclophane, which has a lifetime of more than 500 ps in the S1 state.

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Section: Resultsmentioning

confidence: 99%

Pseudo‐Bimolecular [2+2] Cycloaddition Studied by Time‐Resolved Photoelectron Spectroscopy

Brogaard

Boguslavskiy

Schalk

et al. 2011

Chemistry A European J

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“…This is one of the motivations of the present study. Of course, styrene itself also has been extensively studied as a prototype of aryl olefin,3–25 but there seems to be also no widely accepted picture of the photochemical behavior of styrene. This is another motivation to propose a new picture of the photochemical behavior of styrene in the low‐lying excited states.…”

Section: Introductionmentioning

confidence: 99%

Ab initio study on the electronic structures of styrene in the Franck‐Condon region

Amatatsu

2002

J Comput Chem

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The electronic structures of styrene in the Franck-Condon region have been theoretically examined by means of ab initio complete active space self-consistent field (CASSCF) and the second order multireference Møller-Plesset calculations. The optimized structure of styrene in S(0) is planar but the torsional motion of the phenyl group is very floppy. The S(1) state is assigned to the local pi-pi* excitation within the benzene ring. On the other hand, S(2), above S(1) by 0.561 eV, is assigned to a state that resembles the so-called V-state of ethylene. The transition intensity of S(0)-S(1) is weak, while that of S(0)-S(2) is strong. This is in good agreement with the experimental absorption spectrum where the S(0)-S(1) and S(0)-S(2) transitions are in the energy range of 290-220 nm. The optimized geometry of S(1), characterized by an enlarged benzene ring and its vibrational analyses, further justifies the assignment of the S(1) state.

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“…In general, the S 2 states might be expected to exhibit greater sensitivity to the electronic structure of the substituent than do the S 1 states, which decay predominantly as does benzene. Previously reported experimental values of the first and second ππ* state electronic energies [58][59][60][61][62] and the ionization potentials (IP) [63][64][65][66][67] for the molecules studied here are given in Table 3.…”

Section: Photophysics Of Benzenesmentioning

confidence: 99%

“…68 The inclusion of configuration interaction in quantum-chemical calculations of benzene in these four states, degenerate in zeroth order, yields states with energy order L b (S 1 ,B 2u ) < L a (S 2 ,B 1u ) < B a ,B b (E 1u ). 61 Transitions to states B a and B b are electric dipole-allowed, but those to states L a and L b are forbidden for one-photon transitions from the electronic ground electronic state S 0 .L a and L b are vibronically allowed via e g stretching and e g bending modes, respectively. For the molecules studied here (C s or C 2V symmetry), both L a and L b become symmetry-allowed for one-photon transitions from the ground state, but the energetic ordering of L a and L b depends on the nature of the substituents on the phenyl ring.…”

Section: Photophysics Of Benzenesmentioning

confidence: 99%

“…This reversal of the electronic character in S 1 STY was attributed to the presence of off-axis conjugation with the CdC group. 61 The S 0 r S 1 transition moment polarization in φACT is along the axis perpendicular to the φ-CtCH bond (L b ). It changes to almost parallel (L a )t ot h eφ-CdC axis in STY, due to conjugation with the HCdCH 2 group.…”

Section: Photophysics Of Benzenesmentioning

confidence: 99%

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Substituent Effects in Molecular Electronic Relaxation Dynamics via Time-Resolved Photoelectron Spectroscopy: ππ* States in Benzenes

et al. 2002

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Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. Questions? Contact the NRC Publications Archive team atPublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information. NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. NRC Publications Record / Notice d'Archives des publications de CNRC:http://nparc.cisti-icist.nrc-cnrc.gc.ca/eng/view/object/?id=316e48fa-9e40-45c2-af08-952c6eee950f http://nparc.cisti-icist.nrc-cnrc.gc.ca/fra/voir/objet/?id=316e48fa-9e40-45c2-af08-952c6eee950f We study the applicability of femtosecond time-resolved photoelectron spectroscopy to the study of substituent effects in molecular electronic relaxation dynamics using a series of monosubstituted benzenes as model compounds. Three basic types of electronic substituents were used: CdC (styrene), CdO (benzaldehyde), and CtC (phenylacetylene). In addition, the effects of the rigidity and vibrational density of states of the substituent were investigated via both methyl (R-methylstyrene, acetophenone) and alkyl ring (indene) substitution. Femtosecond excitation to the second ππ* state leads, upon time-delayed ionization, to two distinct photoelectron bands having different decay constants. Variation of the ionization laser frequency had no effect on the photoelectron band shapes or lifetimes, indicating that autoionization from super-excited states played no discernible role. From assignment of the energy-resolved photoelectron spectra, a fast decaying component was attributed to electronic relaxation of the second ππ* state, a slower decaying component to the first ππ* state. Very fast electronic relaxation constants (<100 fs) for the second ππ* states were observed for all molecules studied and are explained by relaxation to the first ππ* via a conical intersection near the planar minimum. Although a "floppy" methyl substitution (R-methylstyrene, acetophenone) leads as expected to even faster second ππ* decay rates, a rigid ring substitution (indene) has no discernible effect. The much slower electronic relaxation constants of the first ππ* states for styrene and phenylacetylene are very similar to those of benzene in its first ππ* state, at the same amount of vibrational energy. By contrast, the lifetime of the first ππ* state of indene was much longer, attributed to its rigid structure. The second ππ* state of benzaldehyde has a short lifetime, similar to the other derivat...

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Styrene and phenylacetylene: Electronic effects of conjugating substituents “off” and “on” the axis of a benzene ring

Cited by 49 publications

References 32 publications

Pseudo‐Bimolecular [2+2] Cycloaddition Studied by Time‐Resolved Photoelectron Spectroscopy

Pseudo‐Bimolecular [2+2] Cycloaddition Studied by Time‐Resolved Photoelectron Spectroscopy

Ab initio study on the electronic structures of styrene in the Franck‐Condon region

Substituent Effects in Molecular Electronic Relaxation Dynamics via Time-Resolved Photoelectron Spectroscopy: ππ* States in Benzenes

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