organic papers o3602 Das et al.  C 28 H 42 N 2 O 3 doi:10.1107/S1600536805031363 Acta Cryst. (2005). E61, o3602–o3604 Acta Crystallographica Section E Structure Reports Online ISSN 1600-5368 Bis[4-(n-octyloxy)phenyl]diazene oxide Purak Das, a Debatra Narayan Neogi, a Shailesh Upreti, b Pradip Kumar Mandal c and Pinaki Bandyopadhyay a * a Department of Chemistry, University of North Bengal, Siliguri 734 430, India, b Department of Chemistry, Indian Institute of Technology, Delhi, New Delhi 110 016, India, and c Department of Physics, University of North Bengal, Siliguri 734 430, India Correspondence e-mail: pbchem@rediffmail.com Key indicators Single-crystal X-ray study T = 293 K Mean (C–C) = 0.004 A ˚ Disorder in main residue R factor = 0.071 wR factor = 0.200 Data-to-parameter ratio = 15.7 For details of how these key indicators were automatically derived from the article, see http://journals.iucr.org/e. # 2005 International Union of Crystallography Printed in Great Britain – all rights reserved Zinc-ammonium chloride reduction of 4-(n-octyloxy)nitro- benzene in an aqueous ethanol has yielded the title compound, C 28 H 42 N 2 O 3 . There are two independent mol- ecules in the asymmetric unit; one is in a disordered state, with two components in unequal proportions (60:40). Comment The title compound, (I), belongs to the 4,4 0 -di-n-alkoxy- azoxybenzene series which is well known for mesogenic behavior (Das et al. , 1999). Compound (I) exhibits a smectic C phase followed by a nematic phase on melting (Chistyakov & Chaikowsky, 1969). For a proper understanding of the struc- ture and bonding of the mesophases, a full knowledge of the crystal and molecular structure of the liquid-crystal-forming compound is very useful. The crystal structures of 4,4 0 -di-n- alkoxyazoxybenzenes with alkyl chains C n H 2n+1 (n = 1–3, 5, 7 and 12) have been reported (Kubo et al. , 2005; Chebli & Brisse, 1995; Sciau et al., 1988; Romain et al., 1986; Shivapra- kash et al., 1985; Cotrait et al., 1979). Although preliminary structural information on the nematic phase of (I) at 383 K has appeared in the literature (Chistyakov & Chaikovskii, 1973), the single-crystal X-ray analysis of (I) has not been reported so far. Against this background, we report here the crystal structure of (I). The asymmetric unit of (I) is shown in Fig. 1. There are two independent molecules, one of them having disorder in the azoxy group. They are related through a pseudo-twofold axis, which passes nearly through the azoxy group and is in the molecular plane. A very similar disorder has been observed in 4,4 0 -azoxydianisole (Chebli & Brisse, 1995). The disorder in the azoxy group in (I) can be explained by assuming that approximately 60% of the molecules in an  orientation are superimposed on 40% of the molecules in a  orientation (consider atom C29 as the  end and C56 as the  end). The N N and N—O bond lengths (Table 1) of (I), derived from the non-disordered molecule, are typical of trans aromatic azoxy compounds (Ejsmont et al., 2000). Two characteristic features of trans aromatic azoxy compounds appear in the geometry of the C12—N1—N2(O1)—C15 fragment. The C15—N2(O1) bond is longer than C12—N1 bond by ca Received 20 September 2005 Accepted 3 October 2005 Online 12 October 2005