Inertial axis reorientation in the <i>S</i>1←<i>S</i> electronic transition of 2-pyridone. A rotational Duschinsky effect. Structural and dynamical consequences

Held, A.; Champagne, B.; Pratt, David W.

doi:10.1063/1.461209

Cited by 124 publications

(135 citation statements)

References 18 publications

(14 reference statements)

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“…22 These were interpreted as two different electronic origins corresponding to two structural isomers in the excited state. 23 Following this, the band at 86 cm −1 is assigned as another electronic origin. These two peaks are sensitive to backing pressure just as in the case of 2-pyridone electronic origin bands.…”

Section: -Methyl-2"1h…pyridone "3mpy…mentioning

confidence: 99%

Spectroscopic studies on methyl torsional behavior in 1-methyl-2(1H)-pyridone, 1-methyl-2(1H)-pyridinimine, and 3-methyl-2(1H)-pyridone. I. Excited state

Sinha

Pradhan

Wategaonkar

et al. 2007

The Journal of Chemical Physics

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The laser induced fluorescence excitation and dispersed fluorescence spectra of three nitrogen heterocyclic molecules 1-methyl-2͑1H͒pyridone ͑1MPY͒, 1-methyl-2͑1H͒pyridinimine ͑1MPI͒, and 3-methyl-2͑1H͒pyridone ͑3MPY͒ have been studied under supersonic jet cooled condition. The methyl torsional and some low frequency vibrational transitions in the fluorescence excitation spectrum were assigned for 1MPY. These new assignments modify the potential parameters to the methyl torsion reported earlier. Some striking similarities exist between the torsional and vibrational transitions in the fluorescence excitation spectra of 1MPY and 1MPI. Apart from pure torsional transitions, a progression of vibration-torsion combination bands was observed for both these molecules. The excitation spectrum of 3MPY resembles the spectrum of its parent molecule, 2-pyridone. The barrier height of the methyl torsion in the excited state of 3MPY is highest amongst all these molecules, whereas the barrier in 1MPI is higher than that of 1MPY. To get an insight into the methyl torsional barrier for these molecules, results of the ab initio calculations were compared with the experimental results. It was found that the conformation of the methyl group undergoes a 60°rotation in the excited state in all these molecules with respect to their ground state conformation. This phase shift of the excited state potential is attributed to the * -* hyperconjugation between the out-of-plane hydrogen of the methyl group and the molecular frame. It has been inferred that the change in lowest unoccupied molecular orbital energy plays the dominant role in the excited state barrier formation.

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Section: -Methyl-2"1h…pyridone "3mpy…mentioning

confidence: 99%

Spectroscopic studies on methyl torsional behavior in 1-methyl-2(1H)-pyridone, 1-methyl-2(1H)-pyridinimine, and 3-methyl-2(1H)-pyridone. I. Excited state

Sinha

Pradhan

Wategaonkar

et al. 2007

The Journal of Chemical Physics

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“…Unlike uracil and thymine, 2PY presents only one cis-amide function, which dramatically reduces the number of possible dimers formed with other nucleobases. Furthermore, 2PY is a UV chromophore whose S 1 (ππ * ) state exhibits a fluorescence lifetime of τ f l = 9 ± 1 ns, 15 which allows both efficient excitation/ionization and high-resolution UV spectroscopy. 15 We have previously employed 2PY to probe the properties of antiparallel double H-bonds formed with 2-aminopyridine, 16 with fluorobenzenes, 17 with uracil, fluorouracil, thymine and other methyluracils, 18,19 and with 9-methyladenine.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, 2PY is a UV chromophore whose S 1 (ππ * ) state exhibits a fluorescence lifetime of τ f l = 9 ± 1 ns, 15 which allows both efficient excitation/ionization and high-resolution UV spectroscopy. 15 We have previously employed 2PY to probe the properties of antiparallel double H-bonds formed with 2-aminopyridine, 16 with fluorobenzenes, 17 with uracil, fluorouracil, thymine and other methyluracils, 18,19 and with 9-methyladenine. 20 The dimer of keto-amino Cyt with 2PY can be viewed as a model of the Cyt:uracil mismatch base-pair, which has been observed in crystal structures of RNAs and RNA duplexes.…”

Section: Introductionmentioning

confidence: 99%

Watson–Crick and Sugar-Edge Base Pairing of Cytosine in the Gas Phase: UV and Infrared Spectra of Cytosine·2-Pyridone

2014

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While keto-amino cytosine is the dominant species in aqueous solution, spectroscopic studies in molecular beams and in noble gas matrices show that other cytosine tautomers prevail in apolar environments. Each of these offers two or three H-bonding sites (Watson-Crick, Wobble, Sugar-edge). The mass-and isomer-specific S 1 ← S 0 vibronic spectra of cytosine·2-pyridone (Cyt·2PY) and 1-methylcytosine·2PY are measured using UV laser resonant twophoton ionization (R2PI), UV/UV depletion and IR depletion spectroscopy. The UV spectra of the Watson-Crick and Sugar-edge isomers of Cyt·2PY are separated using UV/UV spectral holeburning. Five different isomers of Cyt·2PY are observed in a supersonic beam. We show that the Watson-Crick and Sugar-edge dimers of keto-amino cytosine with 2PY are the most abundant in the beam, although keto-amino-cytosine is only the third most abundant tautomer in the gas phase. We identify the different isomers by combining three different diagnostic tools: (1) Methylation of the cytosine N1-H group prevents formation of both the Sugar-edge * To whom correspondence should be addressed 1 and Wobble isomers and gives the Watson-Crick isomer exclusively. (2) Calculation of ground state binding and dissociation energies, the relative gas-phase abundances, the excitation and the ionization energies are in agreement with the assignment of the dominant Cyt·2PY isomers to the Watson-Crick and Sugar-edge complexes of keto-amino cytosine. (3) The comparison of calculated ground state vibrational frequencies to the experimental IR spectra in the carbonyl stretch and NH/OH/CH stretch ranges strengthen this identification.

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“…The emitted fluorescence is collected with an f=150 mm quartz UV lens, collimated onto a UV reflective plane mirror and focused on the horizontal entrance slit of a Hamamatsu C5680-21 ps streak camera with an f=75 mm UV quartz a ±2 ns (1σ) uncertainty, which is twice that indicated in refs. [17] and [18]. In this case, the differences relative to the ps streak camera measurement lie within ±2σ for 2PY and (2PY) 2.…”

Section: Picosecond Streak Cameramentioning

confidence: 73%

“…[17,18] Furthermore, we investigated two isomers of the 2-pyridone trimer (2PY) 3 , denoted A and B, and the (2PY) 4 homo-tetramer, which have been identified and assigned by resonant two-photon ionization spectroscopy. [19] All species were excited at their respective for the low-symmetry (2PY) 3 isomer A, 30988 cm -1 for the high-symmetry (2PY) 3 isomer B and 30572 cm -1 for the (2PY) 4 homo-tetramer.…”

Section: -Pyridone Clustersmentioning

confidence: 99%

Gas-phase Lifetimes of Nucleobase Analogues by Picosecond Pumpionization and Streak Techniques

Blaser

Frey

Heid

et al. 2014

Chimia

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The picosecond (ps) timescale is relevant for the investigation of many molecular dynamical processes such as fluorescence, nonradiative relaxation, intramolecular vibrational relaxation, molecular rotation and intermolecular energy transfer, to name a few. While investigations of ultrafast (femtosecond) processes of biological molecules, e.g. nucleobases and their analogues in the gas phase are available, there are few investigations on the ps time scale. We have constructed a ps pump-ionization setup and a ps streak camera fluorescence apparatus for the determination of lifetimes of supersonic jet-cooled and isolated molecules and clusters. The ps pump-ionization setup was used to determine the lifetimes of the nucleobase analogue 2-aminopurine (2AP) and of two 2AP·(H 2 O) n water cluster isomers with n=1 and 2. Their lifetimes lie between 150 ps and 3 ns and are strongly cluster-size dependent. The ps streak camera setup was used to determine accurate fluorescence lifetimes of the uracil analogue 2-pyridone (2PY), its self-dimer (2PY) 2 , two isomers of its trimer (2PY) 3 and its tetramer (2PY) 4 , which lie in the 7-12 ns range.

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Inertial axis reorientation in the S1←S electronic transition of 2-pyridone. A rotational Duschinsky effect. Structural and dynamical consequences

Cited by 124 publications

References 18 publications

Spectroscopic studies on methyl torsional behavior in 1-methyl-2(1H)-pyridone, 1-methyl-2(1H)-pyridinimine, and 3-methyl-2(1H)-pyridone. I. Excited state

Spectroscopic studies on methyl torsional behavior in 1-methyl-2(1H)-pyridone, 1-methyl-2(1H)-pyridinimine, and 3-methyl-2(1H)-pyridone. I. Excited state

Watson–Crick and Sugar-Edge Base Pairing of Cytosine in the Gas Phase: UV and Infrared Spectra of Cytosine·2-Pyridone

Gas-phase Lifetimes of Nucleobase Analogues by Picosecond Pumpionization and Streak Techniques

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