The crystal structure of a metastable polymorph of para-azoxyanisole

Abstract

The crystal structure of p-azoxyanisole Form I has been determined from synchrotron X-ray powder diffraction data collected at 353 K using simulated annealing.

Probing Crystal Nucleation from Fluid Phases: The Nucleation of para-Azoxyanisole from Its Nematic Liquid Crystalline State

“…Its birefringence changed at the lower temperature of 60 °C (Figure 2e) presumably as a result of a solid state phase transformation. 17,20 No further changes were observed.…”

“…The detailed crystal structure of the stable form (III) was determined by Krigbaum, Chatani and Barber in 1970, 14 Carliste and Smith in 1971 15 and Chebli and Brisse in 1995. 16 The crystal structure of the metastable polymorph (I) has only been reported recently 17 and this is an important factor in enabling further understanding of nucleation in this system. 18 More extensive thermal studies 19,20 of this * To whom correspondence should be addressed.…”

DFT Studies of Selected Epoxies with Mesogenic Units–Impact of Molecular Structure on Electro-Optical Response

“…That negative anisotropy was commonly attributed to the presence of a polar azoxy group in the mesogen, with dipole moment perpendicular to the molecular axis. Even though the first papers on PAA were published in the 1950s, it continues to attract research interest in both the experimental and theoretical field [ 18 , 19 , 20 , 21 , 22 , 23 ]. In comparison with PAA, the structure of AU12 contains additional carboxyl groups at both ends of the mesogen and aliphatic chains terminated with polar epoxy groups.…”

“…In this case, there are only two key dihedral angles, because both phenyl rings in the mesogen are coplanar with the azoxy group. This is also a property of PAA [ 20 , 21 , 22 , 23 ] and added carboxyl groups do not disrupt that coplanarity. However, the carboxyl groups themselves are not coplanar with the phenyl rings; their orientation is given by dihedral angles δ 1 and δ 2 ( Figure 1 ), with energy minima located near ±120° and ±60° ( Figure 3 ).…”

Polymorphism Solvatomorphism 2008

“…Besides the papers just discussed, the 2008 literature contained a large number of additional reports on the polymorphism associated with a wide variety of organic compounds. While some of these substances may be of limited pharmaceutical interest, the references summarized in Table 1 66–110 will be of interest to suitably directed investigators.…”