Journal ArticleDOI
Ab initio conformational analysis of 1,2,3,4-tetrahydroquinoline and the high-resolution rotational spectrum of its lowest energy conformer
Kateřina Luková,Radim Nesvadba,Tereza Uhlíková,Daniel A. Obenchain,Dennis Wachsmuth,Jens-Uwe Grabow,Štěpán Urban +6 more
TLDR
High-resolution microwave spectroscopy was used to determine the precise molecular structures of the conformers of THQ, and the experimentally evaluated molecular constants unambiguously define the lowest energy conformer of 1,2,3,4-tetrahydroquinoline.Abstract:
The saturated part of the 1,2,3,4-tetrahydroquinoline (THQ) molecule allows for the possibility of multiple conformers' existence. High-resolution microwave spectroscopy, supported by high-level quantum chemistry calculations, was used to determine the precise molecular structures of the conformers of THQ. Via the MP2 calculations, we were able to discriminate four stable conformations, i.e. two pairs of energetically equivalent enantiomorphic conformers. The results of the calculations also indicate that energetically non-equivalent conformers are separated by a low energy barrier (104 cm−1) that allows for conformational cooling to occur. The high resolution rotational spectrum with resolved hyperfine structure in the frequency range of 7–20 GHz was obtained using both the In-phase/quadrature-phase-Modulation Passage-Acquired-Coherence Technique (IMPACT) and the coaxially oriented beam resonator arrangement (COBRA) to perform Fourier transform microwave (FTMW) spectroscopy. The precise values of the rotational constants, 14N nuclear hyperfine coupling parameters and centrifugal distortion parameters were determined from the measured transition frequencies. Based on our experimental results, only the most stable enantiomeric pair of THQ contributes to the rotational spectrum under the conditions of our experiment as the less stable conformers seem to efficiently relax to the lower energy conformers. Thus the experimentally evaluated molecular constants unambiguously define the lowest energy conformer of 1,2,3,4-tetrahydroquinoline.read more
Citations
More filters
Journal ArticleDOI
Ealamines A-H, a Series of Naphthylisoquinolines with the Rare 7,8'-Coupling Site, from the Congolese Liana Ancistrocladus ealaensis, Targeting Pancreatic Cancer Cells.
Dieudonné Tshitenge Tshitenge,Dieudonné Tshitenge Tshitenge,Dieudonné Tshitenge Tshitenge,Torsten Bruhn,Torsten Bruhn,Doris Feineis,David Schmidt,Virima Mudogo,Marcel Kaiser,Marcel Kaiser,Reto Brun,Reto Brun,Frank Würthner,Suresh Awale,Gerhard Bringmann +14 more
TL;DR: Ealamines A-D exhibited distinct-and specific-antiplasmodial activities, and they displayed pronounced preferential cytotoxic effects toward PANC-1 human pancreatic cancer cells in nutrient-deprived medium, without causing toxicity under normal, nutrient-rich conditions.
Journal ArticleDOI
Conformers of 1,2,3,4 –tetrahydroisoquinoline in S0 and S1: An analysis through potential energy surface, hardness principles and vibrational spectroscopy
TL;DR: In this paper, a conformational search for 1, 2, 3, 4-tetrahydroisoquinoline (THIQ) yields a number of conformers in S0 and S1 states.
Journal ArticleDOI
Investigating the conformers of 1, 2, 3, 4-tetrahydroquinoxaline: A combined theoretical and experimental investigation through potential energy surface studies, FT-IR and UV-Vis absorption measurements
TL;DR: In this article, a twisted conformer with the equatorial orientation of hydrogen atom of both the NH groups and bearing C2 symmetry is computed to be the most stable conformer (C1) in S0.
Journal ArticleDOI
Tautomers of homophthalic anhydride in the ground and excited electronic states: analysis through energy, hardness and vibrational signatures.
TL;DR: The keto-enol tautomerisation in homophthalic anhydride is investigated in the ground and excited electronic states and the energy and hardness profiles with the variation of IRC are opposite to each other, verifying the principle of maximum hardness.
Book ChapterDOI
Conformational Searching with Quantum Mechanics.
TL;DR: This chapter discusses the application of quantum mechanics to conformational searching, with a focus on three key challenges: the generation of ensembles that include a good approximation to a molecule's bioactive conformation at as prominent a ranking as possible; rational analysis and modification of a pre-established bio active conformation in terms of its energetics.
References
More filters
Journal ArticleDOI
Density‐functional thermochemistry. III. The role of exact exchange
TL;DR: In this article, a semi-empirical exchange correlation functional with local spin density, gradient, and exact exchange terms was proposed. But this functional performed significantly better than previous functionals with gradient corrections only, and fits experimental atomization energies with an impressively small average absolute deviation of 2.4 kcal/mol.
Journal ArticleDOI
Inhomogeneous Electron Gas
P. C. Hohenberg,Walter Kohn +1 more
TL;DR: In this article, the ground state of an interacting electron gas in an external potential was investigated and it was proved that there exists a universal functional of the density, called F[n(mathrm{r})], independent of the potential of the electron gas.
Journal ArticleDOI
Gaussian basis sets for use in correlated molecular calculations. I. The atoms boron through neon and hydrogen
TL;DR: In this paper, a detailed study of correlation effects in the oxygen atom was conducted, and it was shown that primitive basis sets of primitive Gaussian functions effectively and efficiently describe correlation effects.
Journal ArticleDOI
Contracted Gaussian basis sets for molecular calculations. I. Second row atoms, Z=11–18
A. D. McLean,G. S. Chandler +1 more
TL;DR: In this article, the contracted Gaussian basis sets for molecular calculations are derived from uncontracted (12,8) and ( 12,9) sets for the neutral second row atoms, Z=11-18, and for the negative ions P−, S−, and Cl−.
Related Papers (5)
Conformational Analysis of Green Apple Flavour: The Gas‐Phase Structure of Ethyl Valerate Validated by Microwave Spectroscopy
Halima Mouhib,Wolfgang Stahl +1 more