Vibronically state-selective photoisomerization in 5-hydroxytropolone

Ensminger, Frederick A.; Plassard, J.; Zwier, Timothy S.; Hardinger, S. A.

doi:10.1063/1.465607

Cited by 27 publications

(20 citation statements)

References 31 publications

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“…Its application to hole burning spectroscopy is analogous to the ultraviolet-ultraviolet hole burning methods employed by our group on 5-hydroxytropolone. 6,7 The infrared OPO, operating at a repetition rate of 20 Hz, is fixed on an infrared resonance of TrOH-H 2 O identified by FDIRS. The ultraviolet laser, operating at 40 Hz, is then tuned through the vibronic transitions of the complex.…”

Section: Methodsmentioning

confidence: 99%

Fluorescence-dip infrared spectroscopy of the tropolone-H2O complex

Frost

Hagemeister

Arrington

et al. 1996

The Journal of Chemical Physics

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Articles you may be interested inInfrared spectroscopy of OH stretching vibrations of hydrogenbonded tropolone(H2O) n (n=1-3) and tropolone (CH3OH) n (n=1 and 2) clusters Ab initio study of the structure of radical cations derived from Hbonded complexes: a comparison between [H2CO.H2O]+. and [H2CO.HF]+. AIP Conf. Proc. 330, 235 (1995); 10.1063/1.47691Vibronic and electronic states of doubly charged H2S studied by Auger and charge transfer spectroscopy and by a b i n i t i o calculations Fluorescence dip infrared spectroscopy ͑FDIRS͒ is used to probe the effect of a solvent water molecule on intramolecular H-atom tunneling in tropolone. As with the bare molecule discussed in paper I, the FDIR spectrum of the tropolone-H 2 O complex is recorded in the O-H and C-H stretch regions. Three OH stretch fundamentals are observed in the spectrum, and can be assigned nominally to a free OH stretch of the water molecule ͑3724 cm Ϫ1 ͒, a hydrogen bonded OH stretch of water ͑3506 cm Ϫ1 ͒, and the OH stretch of tropolone ͑ϳ3150 cm Ϫ1 ͒. The breadth and complexity of the bands is highly mode specific. The free OH stretch transition is sharp ͑1.8 cm Ϫ1 FWHM͒ and has weak combination bands built on it at ϩ73 and ϩ1600 cm Ϫ1 . The former is assigned to a combination band with the in-plane bending mode of the tropolone-H 2 O hydrogen bond, while the latter is the free OH/intramolecular water bend combination band. The water hydrogen-bonded OH fundamental is also a sharp transition which, after correction for the decreased infrared power at its frequency, is clearly the strongest transition in the spectrum. It is flanked by three close-lying satellite bands 13, 23, and 34 cm Ϫ1 above it, and also supports a weak combination band at ϩ69 cm Ϫ1 due to the in-plane intermolecular bending mode. The tropolone OH absorption is in the same frequency region as in the bare molecule, but broadened to over 100 cm Ϫ1 in TrOH-H 2 O. Distinct substructure in the band is present, with spacings reminiscent of those in the water H-bonded OH stretch region. Ab initio calculations on tropolone-H 2 O are carried out at both the MP2 and Becke3LYP levels of theory. Two isomers with similar binding energies and vibrational frequencies are identified. In one isomer ͑isomer I͒, the water molecule serves as a hydrogen-bonded bridge between the tropolone OH and keto groups. In the other ͑isomer II͒, the water molecule is exterior to the tropolone and hydrogen bonded to the keto oxygen. The experimental evidence does not conclusively distinguish between these two possibilities, though the exterior structure seems somewhat more in keeping with the data as a whole.

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Section: Methodsmentioning

confidence: 99%

Fluorescence-dip infrared spectroscopy of the tropolone-H2O complex

Frost

Hagemeister

Arrington

et al. 1996

The Journal of Chemical Physics

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“…We assign the decay of stimulated emission and the concomitant rise in induced absorbance to excited-state intramolecular proton transfer. This assignment is based on the huge precedent established in other aromatic molecules, [27][28][29][30][31] including hypericin. [20][21][22] It is supported by the kinetic relatedness of the stimulated emission to the induced absorbance and by the observation, discussed immediately below, that the decay time of the stimulated emission is comparable to the fluorescence decay of hypocrellin in H 2 SO 4 .…”

Section: Discussionmentioning

confidence: 99%

“…[20][21][22][23][24][25][26] The proximity of the enol and keto groups in organic molecules provides an environment that is propitious for excitedstate intramolecular proton transfer or hydrogen atom transfer (in this article, we use the two terms interchangeably). Malonaldehyde, 27 salicylic acid, 28 3-hydroxyflavone, 29 benzothiazole, 30 and tropolone 31 are but a few of the examples of a litany of species that execute intramolecular excited-state proton transfer. The disposition and the number of enol and keto groups in hypericin are immediately suggestive of the possibility of excited-state intramolecular proton transfer, and we have interpreted our picosecond spectroscopic studies of this molecule in these terms.…”

Section: Introductionmentioning

confidence: 99%

Excited-State Processes in Polycyclic Quinones: The Light-Induced Antiviral Agent, Hypocrellin, and a Comparison with Hypericin

et al. 1996

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Hypocrellin is a naturally occurring perylene quinone that possesses light-induced antiviral activity, most notably against the human immunodeficiency virus (HIV), as does the related molecule, hypericin. Whitelight continuum is employed to examine the excited-state processes in hypocrellin from the picosecond to the nanosecond time scales. These processes are assigned to intramolecular proton transfer, intersystem crossing, and interconversion between different conformations of hypocrellin, which is constrained to be nonplanar in its ground-state owing to its bulky side chains. The ground state of hypocrellin is suggested to be heterogeneous and to be comprised of an equilibrium between at least two tautomeric forms. The results are discussed in terms of the properties of hypericin, which bears marked similarities and differences with respect to hypocrellin, both in terms of its excited-state properties as well as its mode of induced antiviral activity. Disciplines Chemistry | Physical Chemistry CommentsReprinted (adapted) ReceiVed: April 22, 1996; In Final Form: August 2, 1996 X Hypocrellin is a naturally occurring perylene quinone that possesses light-induced antiviral activity, most notably against the human immunodeficiency virus (HIV), as does the related molecule, hypericin. Whitelight continuum is employed to examine the excited-state processes in hypocrellin from the picosecond to the nanosecond time scales. These processes are assigned to intramolecular proton transfer, intersystem crossing, and interconversion between different conformations of hypocrellin, which is constrained to be nonplanar in its ground-state owing to its bulky side chains. The ground state of hypocrellin is suggested to be heterogeneous and to be comprised of an equilibrium between at least two tautomeric forms. The results are discussed in terms of the properties of hypericin, which bears marked similarities and differences with respect to hypocrellin, both in terms of its excited-state properties as well as its mode of induced antiviral activity.

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“…If, however, we consider systems in which the normal and tautomer species are symmetric, or nearly so, this disparity no longer exists or is significantly minimized. 5-Hydroxytropolone (38)(39)(40) presents an excellent example of such a case. Other examples are the double H-atom transfer in naphchthazarin (41) and in the 4,9-dihydroxyperylene-3,10quinone subunit of hypocrellin producing entirely symmetric structures.…”

Section: Introductionmentioning

confidence: 99%

Identification of a Vibrational Frequency Corresponding to H-atom Translocation in Hypericin¶

Showalter¹,

Datta²,

Chowdhury³

et al. 2007

Photochemistry and Photobiology

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Using time-resolved infrared spectroscopy, ab initio quantum mechanical calculations and synthetic organic chemistry a region in the infrared spectrum of triplet hypericin has been found between 1400 and 1500 cm Ϫ1 corresponding to the translocation of the hydrogen atom between the enol and the keto oxygens, O· · ·H· · ·O. This result is discussed in the context of the photophysics of hypericin and of eventual measurements to observe directly the excited-state H-atom transfer. †Abbreviations: RHF, restricted Hartree-Fock; TRIR, time-resolved infrared spectroscopy.

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Vibronically state-selective photoisomerization in 5-hydroxytropolone

Cited by 27 publications

References 31 publications

Fluorescence-dip infrared spectroscopy of the tropolone-H2O complex

Fluorescence-dip infrared spectroscopy of the tropolone-H2O complex

Excited-State Processes in Polycyclic Quinones: The Light-Induced Antiviral Agent, Hypocrellin, and a Comparison with Hypericin

Identification of a Vibrational Frequency Corresponding to H-atom Translocation in Hypericin¶

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