H/D isotopic “self-organization” effects in the infrared spectra of cyclic tetramers of hydrogen bonds: Polarized spectra of 7-azaindole crystals

Flakus, Henryk T.; Pyzik, Aleksandra

doi:10.1016/j.vibspec.2005.12.006

Cited by 8 publications

(14 citation statements)

References 20 publications

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“…Such experiments should give information about the degree of selectivity of relaxation from the initially excited combination bands as well as about the relevance of the different models, which have been used for describing the N-H stretching band shapes of the dimers. 11,14 Recently, we reported on vibrational population kinetics in the enol ground state of 2-͑2Ј-hydroxy-5Ј-methyl-phenyl͒benzotriazole ͑TINUVIN P͒, which exhibits an intramolecular hydrogen bond. Kinetics was monitored following infrared excitation at a fixed wavelength in the broad, nearly structureless O -H¯N stretching band applying subpicosecond infrared-pump/antiStokes resonance Raman-probe spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Mode-selective vibrational redistribution after spectrally selective N–H stretching mode excitation in intermolecular hydrogen bonds

Kozich

Dreyer

Werncke

2009

The Journal of Chemical Physics

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Mode-selective vibrational redistribution after spectrally selective excitation within the highly structured N-H stretching band of the 7-azaindole dimer was observed by subpicosecond infrared-pump/anti-Stokes Raman-probe spectroscopy. Measurements after relaxation of the N-H stretching vibration indicate ultrafast initial population transfer to vibrations with pronounced N-H bending character. From these modes energy is transferred to modes of frequencies below 1000 cm(-1) on a slower time scale of about 3 ps. Tuning the spectrally narrow infrared excitation to the different substructures of the N-H stretching band influences the distribution of populations between the fingerprint modes. Their relative populations are correlated with the contributions of the modes forming the different coupled combination tones of the N-H stretching band. These results provide experimental support to a Fermi resonance model previously used for simulations of the N-H stretching infrared absorption band shape and insight into relaxation from the initially excited combination bands.

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Section: Introductionmentioning

confidence: 99%

Mode-selective vibrational redistribution after spectrally selective N–H stretching mode excitation in intermolecular hydrogen bonds

Kozich

Dreyer

Werncke

2009

The Journal of Chemical Physics

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“…In case 1, the lower intensity spectral branch appears in the higher-frequency range and is generated by the quasi-forbidden vibrational transition, occurring to the excited state of the non-totally symmetric proton stretching vibrations, occurring in the closed hydrogen-bond chain. 48 In case 2, the lower intensity spectral branch appears in the lowerfrequency range. It corresponds with the quasi-forbidden vibrational transition in the closed chain, corresponding with the totally symmetric proton vibrations, whereas the higherfrequency branch of the band is attributed to the non-totally symmetric proton vibrations in the trimer.…”

Section: Theoretical Approach Proposedmentioning

confidence: 97%

“…The ν X–H band shapes in the two types of the trimer spectra are related one with the other by the approximate mirror reflection symmetry. In case 1, the lower intensity spectral branch appears in the higher-frequency range and is generated by the quasi-forbidden vibrational transition, occurring to the excited state of the non-totally symmetric proton stretching vibrations, occurring in the closed hydrogen-bond chain . In case 2, the lower intensity spectral branch appears in the lower-frequency range.…”

Section: Theoretical Approach Proposedmentioning

confidence: 98%

“…• hydrogen-bonded dimers, e.g., arylacetic acids 33−35 and styrylacetic acid 47 • hydrogen-bonded trimers, e.g., AceOxm 20,21 • hydrogen-bonded tetramers, e.g., 7-azaindole 48 and 4methyl-1,2,4-triazole-thione 49 the ν X−H bands are fairly similar to the corresponding spectra of the other group of crystals, i.e., those with open hydrogen-bond chains in their lattices (e.g., crystals diverse amides and thioamides, 43−45 3-and 4-benzaldehyde, 50 indole-3-carboxaldehyde and 3-acetylindole, 51 acetic acid crystals 52 ). In this case, the ν X−H band contours can be treated as a "mirror ref lection" of the corresponding band shapes of systems from point "a".…”

Section: The Ir Spectra Of Hydrogen-bonded Crystalsmentioning

confidence: 99%

“…The "through-space" (TS) coupling generates the low-intensity spectral branch at the lower-frequency band region, while the "tail-to-head" (TH) coupling involving the trimer hydrogen bonds, occurring via electrons, is responsible for the appearance of the lowerintensity branch at the higher-frequency region of the band. 48,49 D. Temperature Effects in the Spectra versus the Vibrational Exciton Model. It seems justified that in order to explain the temperature effects in the IR spectra of cyclic hydrogen-bond trimers the following hypothesis concerning the mechanisms of the spectra generation should be accepted.…”

Section: Theoretical Approach Proposedmentioning

confidence: 99%

See 2 more Smart Citations

H/D Isotopic and Temperature Effects in the Polarized IR Spectra of Hydrogen-Bond Cyclic Trimers in the Crystal Lattices of Acetone Oxime and 3,5-Dimethylpyrazole

2012

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Polarized IR spectra of hydrogen-bonded acetone oxime and 3,5-dimethylpyrazole crystals were measured at 293 and 77 K in the ν(X-H) and ν(X-D) band frequency ranges. These crystals contain molecular trimers in their lattices. The individual crystal spectral properties remain in a close relation with the electronic structure of the two different molecular systems. We show that a vibronic coupling mechanism involving the hydrogen-bond protons and the electrons on the π-electronic systems in the molecules determines the way in which the vibrational exciton coupling between the hydrogen bonds in the trimers occurs. A strong coupling in 3,5-dimethylpyrazole trimers prefers a "tail-to-head"-type Davydov coupling widespread via the π-electrons. A weak through-space exciton coupling in acetone oxime trimers involves three adjacent hydrogen bonds in each cycle. The relative contribution of each exciton coupling mechanism in the trimer spectra generation is temperature and the molecular electronic structure-dependent. This explains the observed difference in the temperature-induced evolution of the compared spectra. The mechanism of the H/D isotopic "self-organization" processes in the crystal hydrogen bonds was also analyzed. The two types of the hydrogen-bond trimers exhibit the same way, in which the H/D isotopic recognition mechanism occurs. In acetone oxime and 3,5-dimethylpyrazole trimers, identical hydrogen isotope atoms exist in these entire hydrogen-bond systems.

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A distortion of the aromatic character of 7-azaindole in solid-state after its N7 protonation: linear polarized IR-spectroscopy of embedded chemicals in nematic host

Котов

2010

J Incl Phenom Macrocycl Chem

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H/D isotopic “self-organization” effects in the infrared spectra of cyclic tetramers of hydrogen bonds: Polarized spectra of 7-azaindole crystals

Cited by 8 publications

References 20 publications

Mode-selective vibrational redistribution after spectrally selective N–H stretching mode excitation in intermolecular hydrogen bonds

Mode-selective vibrational redistribution after spectrally selective N–H stretching mode excitation in intermolecular hydrogen bonds

H/D Isotopic and Temperature Effects in the Polarized IR Spectra of Hydrogen-Bond Cyclic Trimers in the Crystal Lattices of Acetone Oxime and 3,5-Dimethylpyrazole

A distortion of the aromatic character of 7-azaindole in solid-state after its N7 protonation: linear polarized IR-spectroscopy of embedded chemicals in nematic host

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