Density functional based vibrational study of conformational isomers: Molecular rearrangement of benzofuroxan

Rauhut, Guntram; Jarzęcki, Andrzej A.; Pulay, Péter

doi:10.1002/(sici)1096-987x(199703)18:4<489::aid-jcc4>3.0.co;2-p

Cited by 41 publications

(25 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The required scaling factor for ν NO , ~0.92, is indeed the same as determined by Pulay and coworkers50 and consistent with the range generally encountered for molecules of the first row elements 51. Scaling factors for metal–ligand bonds have not been collected.…”

Section: Resultssupporting

confidence: 78%

New Light on NO Bonding in Fe(III) Heme Proteins from Resonance Raman Spectroscopy and DFT Modeling

et al. 2010

View full text Add to dashboard Cite

Visible and ultraviolet resonance Raman (RR) spectra are reported for Fe III (NO) adducts of myoglobin variants with altered polarity in the distal heme pockets. The stretching frequencies of the Fe III -NO and N-O bonds, ν FeN and ν NO , are negatively correlated, consistent with backbonding. However, the correlation shifts to lower ν NO for variants lacking a distal histidine. DFT modeling reproduces the shifted correlations, and shows the shift to be associated with the loss of a lone-pair donor interaction from the distal histidine that selectively strengthens the N-O bond. However, when the model contains strongly electron-withdrawing substituents at the heme β-positions, ν FeN and ν NO become positively correlated. This effect results from Fe III -N-O bending, which is induced by lone pair donation to the N NO atom. Other mechanisms for bending are discussed, which likewise lead to a positive ν FeN /ν NO correlation, including thiolate ligation in heme proteins and electrondonating meso-substituents in heme models. The ν FeN /ν NO data for the Fe(III) complexes are reporters of heme pocket polarity and the accessibility of lone pair, Lewis base donors. Implications for biologically important processes, including NO binding, reductive nitrosylation and NO reduction, are discussed.

show abstract

Section: Resultssupporting

confidence: 78%

New Light on NO Bonding in Fe(III) Heme Proteins from Resonance Raman Spectroscopy and DFT Modeling

et al. 2010

View full text Add to dashboard Cite

show abstract

“…However, in the particular case of the NO stretch mode, known to require a specific scaling factor, the suggested factor of 0.922 was used. 41 Furthermore, in the high wavenumber region the deviations of the frequencies scaled by eqn (1) from the experimental ones were systematically shifted to small wavenumbers (in any case by less than 30 cm À1 ). For this reason, in order to ease comparison with the experimental spectra, we employed a factor of 0.958 for n > 2900 cm À1 .…”

Section: Experimental Section and Computational Methodsmentioning

confidence: 86%

IRMPD spectroscopy of protonated S-nitrosocaptopril, a biologically active, synthetic amino acid

Coletti

Scuderi

et al. 2010

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

S-Nitrosocaptopril, a biologically active S-nitrosothiol, is generated as protonated species and isolated in the gas phase by electrospray ionization coupled to Fourier Transform Ion Cyclotron Resonance (FT-ICR) or ion-trap mass spectrometry. The structural and IR spectroscopic characterization of protonated S-nitrosocaptopril (SNOcapH(+)) is aided by the comparative study of the parent species lacking the NO feature, namely protonated captopril. The study is accomplished by methodologies based on tandem mass spectrometry, namely by energy resolved collision-induced dissociation and infrared multiple-photon dissociation (IRMPD) spectroscopy, backed by density functional theory calculations. IRMPD spectra have been obtained both in the 1000-1900 cm(-1) fingerprint range, using a beamline of the infrared free electron laser (IR-FEL) at the Centre Laser Infrarouge d'Orsay (CLIO), and in the O-H and N-H stretching region (2900-3700 cm(-1)) using the tunable IR radiation of a tabletop parametric oscillator/amplifier (OPO/OPA) laser source. The structural features of the ion have been ascertained by comparison of the experimental IRMPD spectra with the IR transitions calculated for the lowest energy isomers. Evidence is obtained that protonation occurs at the amide carbonyl oxygen which is found to be the thermodynamically most basic site. However, SNOcapH(+) is present as a thermally equilibrated mixture of low-energy structures, with a major contribution of the most stable isomer characterized by a trans relationship of the positively charged OH group with respect to the carboxylic acid functionality on the adjacent proline ring and by an anti conformation at the S-N (partial) double bond, though the energy difference with the analogous trans-syn isomer is less than 1 kJ mol(-1). The highly diagnostic N-O stretching mode has been unambiguously identified, which may be regarded as an informative probe for S-nitrosation features in more complex, biologically active molecules.

show abstract

“…The existence of the dinitroso intermediates could be proven experimentally by vibrational and electronic spectroscopy: Three groups independently measured the IR and UV spectrum of the photochemically induced reaction of benzofuroxan in Xe and Ar matrix isolation (cf ref. 12). The occurence of a number of new bands in the IR spectrum of photolysed benzofuroxan was assigned to ortho-dinitrosobenzene.…”

Section: The Ring-chain Tautomerism Of Benzofuroxansmentioning

confidence: 99%

Quantum Chemical Studies on the Reactivity of Electron-Rich Heterocycles: Benzofuroxans

Rauhut

Eckert

1999

Science Progress

Self Cite

View full text Add to dashboard Cite

Quantum chemical methods enable the investigation of chemical reaction mechanisms and must be considered a powerful tool for gaining a detailed understanding of chemical reactivity. Their state-of-the-art applications, known as ‘computational chemistry’ or ‘molecular modeling’ have been successful in drug design, biotechnology, and many other areas. However, their application to electron-rich heterocycles is hampered by so-called electron-correlation effects. The dramatic developments in computer technology and recent progress concerning the efficiency of quantum chemical algorithms allow for the investigation of these compounds and their reactions. Still, the sensitivity of the electronic structure of these molecules make such a task a subject to high-performance computing. The molecular class off uroxans and benzofuroxans are known as ‘electron-overcrowded’ and could thus not be treated reliably by computational methods at low levels. An overview is presented here that mainly deals with molecular rearrangements of benzofuroxans and nitrobenzofuroxans. Although most of these reactions are known for a long time their detailed mechanisms could not be explained based only on experimental evidence or at least gave rise to repeated speculations about the basic steps of the actual reaction paths. The progress in understanding the reactivity of benzofuroxans by means of computing the transition states of their reaction mechanisms is summarized.

show abstract

Density functional based vibrational study of conformational isomers: Molecular rearrangement of benzofuroxan

Cited by 41 publications

References 19 publications

New Light on NO Bonding in Fe(III) Heme Proteins from Resonance Raman Spectroscopy and DFT Modeling

New Light on NO Bonding in Fe(III) Heme Proteins from Resonance Raman Spectroscopy and DFT Modeling

IRMPD spectroscopy of protonated S-nitrosocaptopril, a biologically active, synthetic amino acid

Quantum Chemical Studies on the Reactivity of Electron-Rich Heterocycles: Benzofuroxans

Contact Info

Product

Resources

About