Full multinuclear magnetic resonance analysis of 2,4‐dinitrofluorobenzene

Abstract

The spin-lattice relaxation times of 13 C revealed their anisotropy components and it was evident that the dipole-dipole contribution of fluorine was an efficient mechanism for C-1 relaxation. The T 1 s of 1 H agreed with the classical description: at low temperature the main contribution is dipole-dipole relaxation and at high temperature the relaxation is dominated by the spin-rotation mechanism. A linear relationship between d 13 C .exp/ and s C using GIAO (hybrid functional B3LYP) was found. 3 J. 13 C, 1 H) and the 1 J.13 C, 13 C) have a relationship with the delocalization energies estimated by the NBO approach.

Cooperative Structure-Directing Effect of Fluorine-Containing Organic Molecules and Fluoride Anions in the Synthesis of Zeolites

“…19 F MAS NMR spectra of samples 2 (beta), 3 (ZSM-50), and O-2 (ZSM-50) are presented in Figure . The signal at −114 ppm that can be observed in the spectra of the sample O-2 (ZSM-50) is due to the fluorine atom bonded to aromatic carbon in the ortho position, − which is additional evidence that indicates that o -FDBDM is occluded intact (Figure ). The 19 F MAS NMR signal at low field corresponds to fluoride anions that compensate the positive charge of the SDA cations.…”

Beyond excitation NMR relaxation

“…For example, for the flat molecule 2,4-dinitro-fluorobenzene, the chemical shielding anisotropy was found to be related to the spin-lattice relaxation time (95).…”

“…Some spin-lattice relaxation contributions depend on the anisotropy (98, 99) of molecular motion, which permits the evaluation of the rotational diffusion tensors as well as the analysis of the moments of inertia (100). For example, for the flat molecule 2,4dinitro-fluorobenzene, the chemical shielding anisotropy was found to be related to the spin-lattice relaxation time (95).…”

Fluorine-Containing Organic Molecules: A New Class of Structure-Directing Agents for the Synthesis of Molecular Sieves

“…The presence of fluorine atoms belonging to the organic compounds occluded inside the microporous crystals has been assessed by 19 F MAS NMR, Figure . Signals in the region between −105 and −120 ppm are assigned to F atoms attached to the aromatic rings. − Interestingly, three different signals appear in AFI materials, whose relative intensities, but not their position, are strongly modified by the incorporation of silicon into the framework. This complex fluorine NMR signal could eventually be due to different packing orientations of the mF-BP inside the AFI channels.…”