ISSN:
1572-8854
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
,
Physics
Notes:
Abstract The crystal and molecular structure of the title compound hexamethyl-perhy-drotetraazapyrene (I) has been determined by X-ray diffraction methods. The compound crystallizes in the triclinic system, space groupP¯1, with cell dimensionsa=7.715(1),b=10.580(2),c=11.926(2) Å, andα=94.37(1)°,β=104.87(1)°, and γ=107.27(1)°. Since the usual direct methods failed, the structure was solved by a semiempirical optimization of packing a model ofI in the unit cell, in terms of the van der Waals' intermolecular energy. The atomic parameters at the most energetically favored position were then refined by least squares against 2396 observed unique reflections, giving a finalR of 0.067. The semiempirical solution used here seems to be limited to particular cases. The molecule ofI consists of two fused piperazine and two fused hexahydropyrimidine rings, having slightly distorted chair conformations. The rings form a foldedcis-10b,10c system of almost exactC 2 point group symmetry. The lone methyl groups in positions 3 and 8 (at the folding) are found to be axially attached. The geminal methyl groups in positions 1 and 6 are situated away from the folding.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01161113