Solid-state phase transition in triethylenediamine, N(CH₂CH₂)₃N. I. The crystal structure of phase II at 298 K

Crystal Engineering Using Bisphenols. Chains, Ladders and Sheets Formed by the Adducts of 1,4-Diazabicyclo[2.2.2]octane with Bisphenols: Structures of Adducts with 4,4'-Isopropylidenediphenol (1/1), 4,4'-Oxodiphenol (1/1) and 4,4'-Thiodiphenol (1/1 and 2/1)

“…A very similar conclusion was reached concerning the internal motion of the [2.2.2]bicyclooctane cage in [2.2.2]bicyclooctane-1,4-dicarboxylic acid (Ermer & Dunitz, 1969). On the other hand, a neutron diffraction study (Nimmo & Lucas, 1976) of the hexagonal phase II of pure DABCO concluded that the space group was P63/m, which with Z = 2 indicates that the molecules in that phase lie on sites having D3h symmetry and that the molecules are ordered, so that the N--C---C--N torsion angles must be identically zero. In the 2:1 adduct of phenol with DABCO the N---C---C--N torsional angles were found to range from 2.7 (6) to 4.0 (6) ° , while those in the 1:1 adduct of hydroquinone with DABCO ranged from -0.5(6) to 3.1 (6) ° (Mak, Yip & Book, 1984): these values indicate a small but real distortion from (5), viewed along the a axis; H atoms bonded to carbon are omitted.…”

“…The other distances in the bisphenol units are typical of their types. The different structure determinations for pure DABCO, although yielding very similar values for the C--N bond length [solid state 1.470(7) (Nimmo & Lucas, 1976), gas phase 1.472(7)/~ (Yokozeki & Kuchitsu, 1971)], give rather different values for the C--C distance [solid state 1.513 (5), gas phase 1.562 (9)/~,]. The mean C--N and C--C distances found for the DABCO components in adducts (1), (2), (3) and (5) ( Table 3) are all very close to the values found for pure DABCO.…”

“…The conformational properties of the DABCO molecule have been extensively investigated, both in the solid state (Weiss, Parkes, Nixon & Hughes, 1964;Nimmo & Lucas, 1976;Mak, Yip & Book, 1984) and in the gas phase (Yokozeki & Kuchitsu, 1971). The principal point of interest is the extent of any twist of the molecule from ideal Dsh symmetry by internal rotation about the N...N vector: in the D3t~ conformation the neighbouring CH2 groups are all eclipsed.…”

Molecular dynamics in solid 1,4-diazabicyclo[2.2.2]octane perchlorate and hemiperchlorate

“…. They have been extensively studied using N.M.R., N.Q.R., I.R., X-ray and calorimetric techniques [1][2][3][4][5][6][7][8][9]. DABCO, which has molecular symmetry of Dah below 351 K and D 3 above it, exists in three solid phases in which different dynamic behaviour is apparent.…”

Comments onThe rigid-body vibrations of molecules in crystalsby Burns, Ferrier & McMullan (1967)

“…A probable mishandling of the thermal parameters of C(l 1) causing a discrepancy of 0.8a in U °. (Caron, Riche, Pascard-Billy & Gramain, 1977;Caron, Pascard, Agami & Kasakos, 1978;Brisse & Perez, 1976;Nimmo & Lucas, 1976) and has also been cited in text books (e.g. Willis & Pryor, 1975).…”