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Conformational isomerism

About: Conformational isomerism is a research topic. Over the lifetime, 11563 publications have been published within this topic receiving 199312 citations.


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Journal ArticleDOI
TL;DR: In this article, a normal coordinate analysis was used to calculate the vibrational frequencies for the s-trans, gauche and syn conformers of the isoprene (2-methyl-buta-1,3-diene) molecule.

47 citations

Journal ArticleDOI
TL;DR: The most significant finding of this study is the first-time observation of a N-H···π bound conformer of a dimer, which wins over a conventional hydrogen-bonded Conformer of the dimer.
Abstract: In this study, we have explored the conformational landscape of the indole···furan dimer in a supersonic jet by using resonant two-photon ionization (R2PI) and IR-UV double-resonance spectroscopic techniques combined with dispersion-corrected density functional theory (DFT) calculations. Only one conformer of the dimer has been observed in the experiment. DFT/B97-D level calculation shows that N–H···π hydrogen-bonded conformer (T′) is energetically more stable than the N–H···O hydrogen-bonded conformer (HB). Natural bond orbital (NBO) calculation also shows that the hydrogen-bonding interaction in the HB conformer is very weak. Finally, the structure of the observed dimer has been determined to be tilted T-shaped N–H···π hydrogen-bonded (T′) from very excellent agreement between experimental and theoretical N–H stretch frequency. The most significant finding of this study is the first-time observation of a N–H···π bound conformer of a dimer, which wins over a conventional hydrogen-bonded conformer of the ...

47 citations

Journal ArticleDOI
TL;DR: The results show a restriction of the conformational flexibility of the peptide chain after introduction of an N-substituted amino acid, which makes beta sheet formation more difficult.
Abstract: A systematic conformational analysis on several model peptides with N-substituted amino acids was performed on the basis of ab initio MO theory at the HF/6-31G* and HF/3-21G levels with inclusion of solvation effects to study the influence of N-substitution on the formation of typically secondary structural elements, e.g. beta sheets, helices and turns. The conformational flexibility of some structures was examined by means of molecular dynamics simulations in the gas phase and in solution. The results show a restriction of the conformational flexibility of the peptide chain after introduction of an N-substituted amino acid. N-substitution makes beta sheet formation more difficult. Several consecutive N-substituted amino acids in a sequence lead to conformers different from those found on the energy hypersurface of the corresponding N-unsubstituted peptides. There is a strong tendency to form periodically helical conformations, e.g. the polyglycine II or the alpha helix, which can be extended over several N-substituted amino acid residues. As long as 1<--4 hydrogen bond formation remains possible, the major types of beta turns can be formed with a distinct preference for the betaII and betaVIa turns. The betaI turn in particular is considerably destabilized.

47 citations

Journal ArticleDOI
TL;DR: In this paper, the synthesis of modified Cram-type cavitands bearing one or two fluorescent labels for single-molecule spectroscopic studies of vasekite conformational switching was reported.
Abstract: We report the synthesis of modified Cram-type cavitands bearing one or two fluorescent labels for single-molecule spectroscopic studies of vasekite conformational switching (Scheme 3). Syntheses were performed by stepwise bridging of the four couples of neighboring H-bonded OH groups of resorcin[4]arene bowls (Schemes 2 and 3). The new substitution patterns enable the construction of a large variety of future functional architectures. 1H-NMR Investigations showed that the new partially and differentially bridged cavitands feature temperature- and pH-triggered vasekite conformational isomerism similar to symmetrical cavitands with four identical quinoxaline bridges (Table). It was discovered that vasekite switching of cavitands is strongly solvent-dependent.

47 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023303
2022618
2021217
2020219
2019228
2018268