Spectroscopic Characterization of Structural Isomers of Naphthalene: (E)- and (Z)-Phenylvinylacetylene

Abstract

Near-pure samples of (E)-phenylvinylacetylene ((E)-PVA) and (Z)-phenylvinylacetylene ((Z)-PVA) were synthesized, and their ultraviolet spectroscopy was studied under jet-cooled conditions. The fluorescence excitation and UV-UV holeburning (UVHB) spectra of both isomers were recorded. The S0-S1 origin of (E)-PVA occurs at 33,578 cm(-1), whereas that for (Z)-PVA occurs at 33,838 cm(-1), 260 cm(-1) above that for (E)-PVA. The present study focuses primary attention on the vibronic spectroscopy of (E)-PVA. Single vibronic level fluorescence spectra of many prominent bands in the first 1200 cm(-1) of the S0-S1 excitation spectrum of (E)-PVA were recorded, including several hot bands involving low-frequency out-of-plane vibrations. Much of the ground-state vibronic structure observed in these spectra was assigned by comparison with styrene and trans-beta-methylstyrene, assisted by calculations at the DFT B3LYP/6-311++G(d,p) level of theory. Both S0 and S1 states of (E)-PVA are shown to be planar, with intensity appearing only in even overtones of out-of-plane vibrations. Due to its longer conjugated side chain compared with that of its parent styrene, (E)-PVA supports extensive Duschinsky mixing among the four lowest-frequency out-of-plane modes (nu45-nu48), increasing the complexity of this mixing relative to that of styrene. Identification of the v'' = 0-3 levels of nu48, the lowest frequency torsion, provided a means of determining the 1D torsional potential for hindered rotation about the C(ph)-C(vinyl) bond. Vibronic transitions due to (Z)-PVA were first identified as small vibronic bands that did not appear in the UVHB spectrum recorded with the hole-burn laser fixed on the S0-S1 origin of (E)-PVA. The LIF and UVHB spectra of a synthesized sample of (Z)-PVA confirmed this assignment.

Theoretical study of radiative and non-radiative decay processes in pyrazine derivatives

“…28,29 Recent combined computational and experimental investigations showed that in order to achieve quantitative assignments for single vibronic level fluorescence spectroscopy in phenylvinylacetylene, Duschinsky rotation effects are imperial, which posed computational challenges for quantum chemistry. 37,38 Under the Franck-Condon approximation, the IC rate can be expressed as…”

The excited states and vibronic spectroscopy of diphenyldiacetylene and diphenylvinylacetylene

“…46 This is consistent with what is observed in the corresponding series of C 4 phenyl derivatives, where trans-PVA and PDA are 263 and 2916 cm À1 blue of PBD. 62,64 All three diphenyl molecules in the series undergo rapid internal conversion or intersystem crossing that result in a loss of fluorescence within a few hundred wavenumbers of their origins, though the exact nature of the processes has not been fully determined, and may differ within the series. One of the most notable differences between DPDA, DPVA, and DPBD is the breadth of their transitions in the near-ultraviolet.…”

“…Our recent studies of the spectroscopy and isomerization of trans-and cis-phenylvinylacetylene (PVA) have led to the conclusion that the vinylacetylene substituent produces vibronic spectra similar in many ways to those of styrene and stilbene. 41,42 A reversal of the order of substitution to make 1-phenyl-1-butyn-3-ene (PAV) produces a vibronic spectrum with characteristics similar to those of phenylacetylene. 43 Capping the end of either PVA or PAV with a second phenyl ring produces diphenylvinylacetylene (DPVA).…”

Isomer specific spectroscopy of C10Hn, n = 8–12: Exploring pathways to naphthalene in Titan's atmosphere

“…The cis and trans isomers of 4-phenyl-1-butene-3-yne (phenylvinylacetylene, labeled hereafter as Z-PVA and E-PVA) are one pair of C 10 H 8 isomers recently explored in some detail. 7 Photoisomerization of each of these isomers has also been studied using the newly developed method of ultraviolet population transfer spectroscopy. 8 Here, we report on the ultraviolet spectroscopy of a close analog of PVA in which the order of the ethynyl and vinyl groups relative to the phenyl ring are swapped, 1-phenyl-1-butyne-3-ene, labeled as PAV in order to highlight the re-ordering of the conjugated substituents.…”