Polymorphisme du radical libre nitroxyde tétraméthyl-2,2,6,6-piperidinone-4 oxyl-1. Affinement de la structure de la phase orthorhombique

Crystal structure of 2,6-diphenyl-3-methyl-N-nitrosopiperidin-4-one

“…The crystal structure shows the bond lengths and bond angles of the molecule, the values are in agreement with the values reported for 3,5-dimethyl-2,6-diphenylpiperidin-4-one oxime and other related structures [7][8][9][10]. The carbonyl oxygen bond length (C@O) 1.213(3) Å is comparable with the average value of 1.218(3) Å reported elsewhere [11,12].…”

The shape of the ground and lowest two excited states of H2NO

“…It follows that the compromise between the trends to planar or pyramidal geometries for the ground state is more fragile than ever expected. The geometry of the nitroxide group will actually be determined by the perturbation induced by the substituents, which rationalizes the geometrical changes with the electronegativity of the substituents found in recent theoretical calculations, 18 as well as the large variety of structures, planar 19 or pyramidal 20 observed in x-ray diffraction experiments ͑see Fig. 4 for selected examples͒.…”

Ordering in channel inclusion compounds of TANO with linear-chain compounds. I. High- and low-temperature structures of TANO–n-heptane

“…Examination of the Fourier map led to the conclusion that the TANO frame is disordered too: on each molecular site, we find two different enantiomers of TANO molecules with unequal occupation. As in the other known forms of TANO alone (Bordeaux & Lajzerowicz, 1974;Le Bars-Combe, 1982), the molecule is chiral with a twisted ring, C ~N-O is planar, and C--O and N--O bonds are C almost lined up, constituting a quasi 2 axis for the molecule (Fig. 1).…”

“…The compound obtained, although well crystallized as orange needles, contained a small amount of solvent that we eliminated by heating for a few minutes at 326 K. Then we obtained a yellow powder, corresponding to the orthorhombic form of pure TANO (melting temperature 309 K), the structure of which was refined by Bordeaux & Lajzerowicz (1974).…”

“…Coordinates (A,) of TANO enantiomer A in the local reference system as defined in Fig. 3 C,N,O atom coordinates from the orthorhombic form of TANO (Bordeaux & Lajzerowicz, 1974 ution. The same may be true in the solid TANO-nheptane compound but X-rays, which cannot distinguish the static or dynamic aspect of the disorder, do not permit a conclusion to be reached.…”