Structure de la forme C de la naphtazarine

A further investigation of the crystal structures of naphthazarin

“…Unsymmetrical derivatives show the number and pattern of signals expected from the supposed formula, but naphthazarin itself shows one signal only for the carbon-bound hydrogen atoms, and thus on a 3"81 A 3"74 3"75 3"743 + 0"004 Pascard-Billy, 1962d), which was based on three-dimensional photographic data, had not proceeded beyond the assumption of isotropic thermal motion, and in the belief that the full potential of these data had not been realized, this refinement was further continued.…”

“…Naphthazarin exists in three crystalline modifications, which have been the subject of numerous studies (Palacios & Silva, 1938;Billy, 1955Billy, , 1958Borgen, 1956;Watase, Osaki & Nitta, 1957;Srivastava, 1958Srivastava, , 1959Srivastava, , 1961Golder & Zhdanov, 1958;Pascard-Billy, 1961, 1962a. The structures of all three are in space group P2Jc (or equivalent), and are such that the molecules are required to be centrosymmetric.…”

Structures of nitrogen-containing aromatic compounds. IV. 1,4,5,8-Pyridazino[1,2-a]pyridazinetetrone

“…Were the molecule exactly planar, the O atoms would be forced together, thus producing large compression strains. This energetically unfavourable situation is found in the geometrically comparable molecule naphthazarin (Pascard-Billy, 1962;Cradwick & Hall, 1971) (Table 5). Because the asymmetric unit consists of three chemically identical yet crystallographically unique molecules, there are several independent measures of the same bond lengths, e.g.…”

1H and2H NMR Relaxation in Hydrogen-Bonded Solids Due to a Complex Motion: Classical Jumps over a Barrier and Incoherent Tunneling

“…1b) or as a one-step two-proton transfer proceeding ation time is determined by homonuclear dipolar interactions through the centrosymmetric species (Fig. 1c) (4). Howand, according to the well-established theory, the motional ever, theoretical calculations (2,10) show that the interconspectrum of the hydrogen atom is sampled at the proton version of the two minimum energy tautomers has one absoLarmor frequency v I and at 2v I .…”

“…The polymorphs of naphthazarin have and 3. The minimum corresponding to configuration 1 is been studied extensively by using infrared, Raman, 13 C the deepest, while the other two minima are of almost NMR, and neutron and X-ray diffraction methods (2)(3)(4)(5)(6)(7)(8)(9)(10). equal depth ( 13 ) .…”