Quantum-Induced Symmetry-Breaking in the Deuterated Dihydroanthracenyl Radical

Krechkivska, Olha; Wilcox, Callan M.; Nauta, Klaas; Kable, Scott H.; Schmidt, Timothy W.

doi:10.26434/chemrxiv.8123648

Cited by 1 publication

(3 citation statements)

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“…From the assignments in Figure 11, we determine a scaling factor of 0.958 for the calculated cis-MVB D 1 frequencies (Supporting Information, Section S6); this is consistent with results for similar systems, 20,21,31,32 giving us confidence in our analysis. Nevertheless, several assignments must be closely reasoned.…”

Section: Detailed Assignments and Discussionsupporting

confidence: 84%

“…Some frequencies derive from tentative assignments, particularly for weak bands in congested regions. Nevertheless, the scaling factor is again consistent with other RSRs20,21,31,32 and is not dissimilar to that found for cis-MVB (0.958), which was determined from relatively few assignments.…”

supporting

confidence: 88%

“…In Franck−Condon simulations, the B3LYP D 0 frequencies of 47 small-amplitude modes were scaled by 0.97, in accordance with usual practice for hydrocarbon RSRs. 20,29,30 While various scaling factors in the range 0.95−0.97 have previously been used 20,21,31,32 for excited states, we have left all D 1 frequencies unscaled. All calculations were performed with the Gaussian 09 suite of electronic structure programs.…”

Section: Computational Detailsmentioning

confidence: 99%

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Electronic Spectroscopy of cis- and trans-meta-Vinylbenzyl Radicals

et al. 2021

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Resonance-stabilized radical (RSR) isomers of C 9 H 9 persist in complex energetic environments such as flames and plasmas derived from aromatic precursors. Of the myriad possible C 9 H 9 RSRs, only 1-indanyl (the global minimum) and 1-phenylallyl have been conclusively identified spectroscopically. Electronic spectra near 600 nm, close to several DIBs, were recently reported by the group of Maier for C 9 H 9 products of a heptadiyne discharge. They were tentatively ascribed to isomers of vinylbenzyl on the basis of computed transition energies and ionization potentials, the best agreement with the latter property (ca. 7.3 eV) provided by the meta isomer. To further examine this conjecture, we have undertaken surveys for the electronic spectra of o-,m-, and p-vinylbenzyl radicals in discharges of vinyltoluenes, using resonant two-color ionization and fluorescence spectroscopy. In a jet-cooled discharge of m-vinyltoluene, we have detected cisand transm-vinylbenzyl radicals near 525 nm. We observe adiabatic ionization energies (ca. 7.15 eV) for both conformers that are comfortably bracketed by B3LYP (7.11 eV) and CBS-QB3 (7.22 eV) calculations, from which we conclude that the carrier of the 600 nm spectrum remains unidentified. Optical-optical holeburning spectroscopy has been used to untangle cis and trans features of m-vinylbenzyl. There is very little to distinguish the two conformers from calculations, thermochemically or spectroscopically: they are similarly stable, their ground and excited state equilibrium geometries are planar, and their electronic transition energies, AIEs, predicted rotational contours, and excited state vibrational frequencies are highly similar. The most significant point of difference is a large (for cis) and relatively small (for trans) increase in the vinyl torsion force constant upon excitation, strongly suggesting identification of the cis conformer from an origin dispersed fluorescence spectrum, acceptance of which identification allows several other ground-state assignments to fall into place. A considerable breakdown in mirror symmetry between excitation and emission spectra for a modes is tentatively attributed to interference between Franck-Condon and Herzberg-Teller contributions to the transition moment, the low symmetry of the molecule (C s ) placing little restriction on such an interaction.

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Section: Detailed Assignments and Discussionsupporting

confidence: 84%

supporting

confidence: 88%