(E,E)-1,1'-[1,2-Bis(4-chlorophenyl)ethane-1,2-diyl]bis(phenyldiazene) revisited: threefold configurational disorder of (S,S), (R,R) and (S,R) isomers, a detailed critique

Sean Parkin; Christopher Glidewell; Peter N Horton

doi:10.1107/S2053229623001262

(E,E)-1,1'-[1,2-Bis(4-chlorophenyl)ethane-1,2-diyl]bis(phenyldiazene) revisited: threefold configurational disorder of (S,S), (R,R) and (S,R) isomers, a detailed critique

Acta Crystallogr C Struct Chem. 2023 Mar 1;79(Pt 3):77-82. doi: 10.1107/S2053229623001262. Epub 2023 Feb 15.

Authors

Sean Parkin¹, Christopher Glidewell², Peter N Horton³

Affiliations

¹ Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055, USA.
² School of Chemistry, University of St Andrews, Fife, KY16 9ST, United Kingdom.
³ School of Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, United Kingdom.

PMID: 36871289
DOI: 10.1107/S2053229623001262

Abstract

Crystal structures described as concomitant triclinic (I) and monoclinic (II) polymorphs of meso-(E,E)-1,1'-[1,2-bis(4-chlorophenyl)ethane-1,2-diyl]bis(phenyldiazene) [Mohamed et al. (2016). Acta Cryst. C72, 57-62] have been re-investigated. The published model for II was distorted due to forcing the symmetry of space group C2/c on an incomplete structure model. It is shown here to be a likely three-component superposition of S,S and R,R enantiomers with a lesser amount of the meso form. A detailed analysis of how the improbable distortion in the published model aroused suspicion and the subsequent construction of undistorted chemically and crystallographically plausible alternatives having the symmetry of Cc and C2/c is presented. For the sake of completeness, an improved model for the triclinic P-1 structure of the meso isomer I, revised to include a minor disorder component, is also given.

Keywords: configurational disorder; correction; crystal structure; polymorphism; whole-molecule disorder.