Preresonance Raman spectra for imidazole and imidazolium ion: interpretation of the intensity enhancement from a precise assignment of normal modes

Majoube, M.; Henry, M.O.; Chinsky, L.; Turpin, Pierre‐Yves

doi:10.1016/0301-0104(93)80080-s

Cited by 39 publications

(49 citation statements)

References 14 publications

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“…Computed frequencies and isotope shifts were in reasonable agreement with experiment and with previous computations 9,10,16,17,30,31,33,36 for ImH 2 + (Table S2), ImH (Table S3), Im − (Table S4) MeImH 2 + (Table S5), MeImH (τ tautomer, Table S6 and π tautomer, Table S7) and MeIm − (Table S8). The experimental frequencies (including weakly enhanced bands obtained with pre-resonant (488 nm) excitation together with 15 N and C 2 D isotopic shifts (Figure S1–S3)) are correlated across the three protonation states in Tables 1 and 2, while measured cross sections are listed in Table 3…”

Section: Resultssupporting

confidence: 87%

Mode Recognition in UV Resonance Raman Spectra of Imidazole: Histidine Monitoring in Proteins

Balakrishnan

Jarzęcki

et al. 2012

J. Phys. Chem. B

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The imidazole side-chains of histidine residues perform key roles in proteins, and spectroscopic markers are of great interest. The imidazole Raman spectrum is subject to resonance enhancement at UV wavelengths, and a number of UVRR markers of structure have been investigated. We report a systematic experimental and computational study of imidazole UVRR spectra, which elucidates the band pattern, and the effects of protonation and deprotonation, of H/D exchange, of metal complexation, and of addition of a methyl substituent, modeling histidine itself. A consistent assignment scheme is proposed, which permits tracking of the bands through these chemical variations. The intensities are dominated by normal mode contributions from stretching of the strongest ring bonds, C2N and C4C5, consistent with enhancement via resonance with a dominant imidazole π-π* transition.

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Section: Resultssupporting

confidence: 87%

Mode Recognition in UV Resonance Raman Spectra of Imidazole: Histidine Monitoring in Proteins

Balakrishnan

Jarzęcki

et al. 2012

J. Phys. Chem. B

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“…The vibrational spectral assignments were carried out with the aid of NCA followed by force field calculation with the same level of theory that was employed for the geometry optimization of the (14), ω CHar (14), CNCsci (11), ω C 1 C 7 (10), νC 7 (15), ω C 1 C 7 (14), Rasyt (11), ω C 7 N 8 (9) 70 0.5 ω C 7 N 8 (45), CNCsci (29), ω C 1 C 7 (10), δC 1 C 7 (5) 42…”

Section: Vibrational Analysismentioning

confidence: 99%

“…This band is experimentally blue-shifted in the Raman spectrum by ca 1580 cm −1 with strong intensity, which is obliviously in the range of the protonated imidazolinium ring. [14] Its counterpart in the IR spectrum at 1578 cm −1 appears to be weak owing to its symmetry. This protonation marker clearly indicates the existence of intermolecular H-bonding or association, which enhances the aromaticity of the imidazole ring.…”

Section: Imidazole Ring Vibrationsmentioning

confidence: 99%

Vibrational spectra and potential energy distributions for 1‐benzyl‐1H‐imidazole by normal coordinate analysis

James¹,

Ravikumar²,

Jayakumar³

et al. 2008

J Raman Spectroscopy

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The Fourier-transform (FT) Raman and infrared (IR) spectra of the crystallized novel pharmaceutical molecule 1-benzyl-1H-imidazole (BI) were recorded and analyzed. The geometry, intermolecular hydrogen bond, and harmonic vibrational wavenumbers of BI were investigated with the help of B3PW91 density functional theory (DFT) methods. The detailed interpretation of the vibrational spectra was carried out with the aid of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMFF). The aromaticities of the imidazole and phenyl rings were studied using the standard harmonic oscillator model of aromaticity (HOMA) index. Natural bond orbital (NBO) analysis on BI was carried out to demonstrate the various intramolecular interactions that are responsible for the stabilization of this molecule leading to its medicinal activity. The potential energy profile corresponding to the torsion around the bridge bonds connecting the two rings was drawn to explain the steric and/or electronic effects using potential energy surface (PES) scan studies. The pronounced double-bond localization in the imidazole ring upon intermolecular H-bonding appears to be the cause for its enhanced aromaticity.

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“…Ł transitions. 6,14,15 Caswell and Spiro 8 found double-peaked RR excitation profiles, with maxima at approximately 218 and 204 nm, suggesting two transitions. However, several theoretical investigations 16 -19 agree that only one of the two imidazole !…”

Section: Introductionmentioning

confidence: 99%

“…Previous computational modeling of the imidazole RR intensity pattern 6,7,14 showed that the enhancement is dominated by the Franck-Condon (A-term) mechanism and that the harmonic approximation to the ground state and the resonant excited state is reasonable. Within this approximation, the resonance Raman intensities are directly related to the forces acting on the resonant excited state within the Franck-Condon region.…”

Section: Introductionmentioning

confidence: 99%

Ab initio computation of the UV resonance Raman intensity pattern of aqueous imidazole

Jarzęcki

Spiro

2001

J Raman Spectroscopy

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The UV resonance Raman (RR) spectrum of aqueous imidazole was modeled by evaluating the gradients of the resonant p → p * excited state, using various levels of theory. To take account of H-bonding effects, two water molecules were included in the model, one accepting an H-bond from and the other donating an H-bond to imidazole. The ground-state geometry and force field of the ImH·2H 2 O complex was computed via SQM-DFT theory, with the B3LYP functional, yielding good agreement with experimental vibrational wavenumbers for the in-plane imidazole modes. Evaluation of excited-state gradients with the semiempirical ZINDO method, which has previously been applied successfully to metalloporphyrin RR spectra, failed to reproduce the imidazole UVRR spectrum. However, the ab initio CIS method gave fairly good results. Agreement with the experimental intensity pattern improved when minimal STO-3G or 3-21G * basis sets were upgraded to 6-31G * , but further refinement, to 6-31G * * , did not alter the pattern, and addition of diffuse functions actually degraded the spectral quality. Likewise, more elaborate levels of ab initio theory, TDDFT and CASSCF(4,4), gave poorer agreement with experiment then CIS. Thus optimum modeling of the UVRR spectrum was achieved with the popular CIS/6-31G * methodology. Application of the Kramers-Kronig transform frequency correction to the ! k 2 approximation ('short-time limit') altered the intensity distribution only slightly.

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Preresonance Raman spectra for imidazole and imidazolium ion: interpretation of the intensity enhancement from a precise assignment of normal modes

Cited by 39 publications

References 14 publications

Mode Recognition in UV Resonance Raman Spectra of Imidazole: Histidine Monitoring in Proteins

Mode Recognition in UV Resonance Raman Spectra of Imidazole: Histidine Monitoring in Proteins

Vibrational spectra and potential energy distributions for 1‐benzyl‐1H‐imidazole by normal coordinate analysis

Ab initio computation of the UV resonance Raman intensity pattern of aqueous imidazole

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