Browsing by Subject "hydrogen bonds"

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    A structural analysis of 2,5-diaryl-4H-2,4-dihydro-3H-1,2,4-triazol-3-ones: NMR in the solid-state, X-ray crystallography and GIPAW calculations
    (Wiley, 2021) Marín-Luna, Marta; Sánchez-Andrada, Pilar; Alkorta, Ibon; Elguero, José; Torralba, M. Carmen; Delgado-Martínez, Patricia; Santa María, Dolores; Claramunt, Rosa M.; Química Orgánica
    The 1H, 13C, 15N, and 19F nuclear magnetic resonance (NMR) spectra of 11 2,5-diaryl-2,4-dihydro-3H-1,2,4-triazol-3-ones have been acquired in DMSO-d6 solution and the 13C, 15N, and 19F NMR spectra have also been acquired in the solid state (solid-state nuclear magnetic resonance [SSNMR] and magic angle spinning [MAS]). The X-ray structures of Compounds 3, 5, and 6 have been determined by X-ray diffraction. Theoretical calculations at the gauge-independent atomic orbital (GIAO)/B3LYP/6-311++G(d,p) level have provided a set of 321 chemical shifts that were compared with 310 experimental values in DMSO-d6. To obtain good agreements, some effects need to be included. The SSNMR chemical shifts have been compared with gauge-including projector-augmented wave (GIPAW) calculations and with the heavy atom–light atom (HALA) effects.
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    Co-conformational Exchange Triggered by Molecular Recognition in a Di(acylamino)pyridine-Based Molecular Shuttle Containing Two Pyridine Rings at the Macrocycle
    (WILEY-VCH VERLAG GMBH, 2016-01-21) Martinez-Cuezva, Alberto; Carro-Guillen, Fernando; Pastor Vivero, Aurelia; Marin-Luna, Marta; Orenes, Raul-Angel; Alajarín, Mateo; Berná Cánovas, José; Química Orgánica
    We describe the incorporation of endo-pyridine units into the tetralactam ring of di(acylamino)pyridine-based rotaxanes. This macrocycle strongly associates with the linear interlocked component as confirmed by X-ray diffraction studies of rotaxane 2b. Dynamic NMR studies of 2b in solution revealed a rotational energy barrier that was higher than that of the related rotaxane 2a, which lacks of pyridine rings in the macrocycle. The macrocycle distribution of the molecular shuttle 4b, containing two endo-pyridine rings, shows that the major co-conformer is that with the cyclic component sitting over the di(acylamino)pyridine station. DFT calculations also support the marked preference of the ring for occupying the heterocyclic binding site. The association of N-hexylthymine with the di(acylamino) pyridine binding site of 4b led to the formation of a rare 'S'-shaped co-conformer in which the tetralactam ring interacts simultaneously with both stations of the thread.