Conformational polymorphism of (E,E)-N,N′-bis(4-nitrobenzylidene)benzene-1,4-diamine

Abstract

Two polymorphs of (E,E)-N,N'-bis(4-nitrobenzylidene)benzene-1,4-diamine, C(20)H(14)N(4)O(4), (I), have been identified. In each case, the molecule lies across a crystallographic inversion centre. The supramolecular structure of the first polymorph, (I-1), features stacking based on π-π interactions assisted by weak hydrogen bonds involving the nitro groups. The second polymorph, (I-2), displays a perpendicular arrangement of molecules linked via the nitro groups, combined with weak C-H···O hydrogen bonds. Both crystal structures are compared with that of the carbon analogue (E,E)-1,4-bis[2-(4-nitrophenyl)ethenyl]benzene, (II).

Quantum chemical study of self-doping PPV oligomers: spin distribution of the radical forms

“…Due to the presence of the two nitrogen atoms next to the central ring, this ring is twisted out of the plane of the peripheral rings and the CH=N spacers by about 40° [14,15]. Consequently, the SO 3 group of the sidechain is able to contact two of the ortho-methoxy groups on the peripheral rings and forms the stabilized structure presented in Fig.…”

“…The benzylidene-aniline (BA) condensation, used to prepare DSBs in which the spacers are CH=N rather than CH=CH [14,15], is one such procedure and oligomers such as 5 and 6 ( Fig. 2) would become available.…”

(E,E)-N1-(2,3,4,5,6-Pentafluorobenzylidene)-N4-(3,4,5-trimethoxybenzylidene)benzene-1,4-diamine

“…For compounds with -conjugated systems and fluorinated rings, see: Coates et al (1998); Adamson et al (1994); Li et al (1994); Ponzini et al (2000); Allaway et al (2002); Collings et al (2004); Papagni et al (2010). For structures of related benzylidine aniline oligomers, see: Collas, De Borger et al (2011); Collas, Zeller & Blockhuys (2011). For a description of the Cambridge Structural Database, see: Allen (2002).…”

“…The nitrogen atoms in the imine spacers and the activated azomethine hydrogen atoms H21 and H41 do not participate in any intermolecular contacts. This may be linked to the absence of the typical twist of the central phenylenediamine Amanova & Blockhuys (2011) and Collas, Zeller & Blockhuys (2011)], as the availability of the nitrogen atom in (I) is reduced. On the other hand, the resulting planar conformation leads to an improved stacking of molecules, notwithstanding the modest packing efficiency of only 68.3%.…”