Structures and short contacts of F center dot center dot center dot O(nitro) and H center dot center dot center dot O(nitro) in 2,2-di(4-nitrophenyl)hexafluoropropane and 2,2-di(4-nitrophenyl)propane

摘要

2,2-Di(4-nitrophenyl)hexafluoropropane (1) and 2,2-di(4-nitrophenyl)propane (2) were synthesized and their crystal structures were determined. The crystals of both diarylpropanes have helical conformations with unsymmetrical ring-twist angles, phi(A) = 46.7, phi(B) = 33.5degrees for 1, and phi(A) = 64.9, phi(B) = 31.8degrees, for 2. In contrast, density functional theory calculations indicate symmetrical, helical C-2 states for both 1 (phi(A) = phi(AB) = 43.1degrees) and 2 (phi(A) = phi(B) = 51.5degrees). Intermolecular pi-pi-stacks along the a-axis of the crystals are composed of a pair of nitrophenyl rings oriented in opposite directions. Short contacts of O(nitro)F-... and O(nitro)H-...(Me) within the sum of van der Waals radii were also found in 1 and 2, respectively. (C) 2002 Elsevier Science B.V. All rights reserved. [References: 21]