p-Stacked hydrogen-bonded sheets in N,N 0 -bis(4-nitrobenzylidene)ethane- 1,2-diamine and p-stacked hydrogen- bonded chains in N,N 0 -bis(4-nitro- benzylidene)propane-1,3-diamine Joao A. S. Bomfim, a James L. Wardell, a John N. Low, b Janet M. S. Skakle b and Christopher Glidewell c * a Instituto de Quõ Âmica, Departamento de Quõ Âmica Inorga Ãnica, Universidade Federal do Rio de Janeiro, 21945-970 Rio de Janeiro, RJ, Brazil, b Department of Chemistry, University of Aberdeen, Meston Walk, Old Aberdeen AB24 3UE, Scotland, and c School of Chemistry, University of St Andrews, Fife KY16 9ST, Scotland Correspondence e-mail: cg@st-andrews.ac.uk Received 17 November 2004 Accepted 23 November 2004 Online 18 December 2004 Molecules of N,N 0 -bis(4-nitrobenzylidene)ethane-1,2-diamine, C 16 H 14 N 4 O 4 , (I), lie across centres of inversion in space group P2 1 /n and are linked into (10 1) sheets by a single CÐHO hydrogen bond [HO = 2.40 A Ê ,CO = 3.2166 (13) A Ê and CÐHO = 146  ]; these sheets are linked into a three- dimensional array by a single aromatic ± stacking interac- tion. Molecules of N,N 0 -bis(4-nitrobenzylidene)propane-1,3- diamine, C 17 H 16 N 4 O 4 , (II), lie across twofold rotation axes in space group C2/c and are linked into chains of spiro-fused rings by a single CÐHO hydrogen bond [HO = 2.54 A Ê , CO = 3.267 (2) A Ê and CÐHO = 130  ]; these chains are linked into sheets by a single aromatic ± stacking interaction. Comment As part of a study of the supramolecular structures of compounds containing nitro groups, the structures of the title compounds were determined. The structure of N,N 0 -bis(4- nitrobenzylidene)ethane-1,2-diamine, (I), has been reported very recently (Sun et al., 2004) and it is clear that the deter- mination reported here refers to the same phase as that in the previous report. A larger data set is employed here (2717 re¯ections as opposed to 1635), leading to slightly higher precision. Although Sun et al. (2004) drew attention to the presence in the structure of a CÐHO hydrogen bond and to the occurrence of an aromatic ± stacking interaction, the structural consequences of these interactions were not analysed or discussed in detail. In particular, the dimension- ality of the resulting supramolecular structure was not speci- ®ed. Accordingly, we feel it is justi®able to discuss this structure in detail along with that of its homologue N,N 0 -bis(4- nitrobenzylidene)propane-1,3-diamine, (II). Molecules of (I) (Fig. 1) lie across centres of inversion in space group P2 1 /n, and the reference molecule was selected to lie across ( 1 2 , 1 2 , 1 2 ). The key torsion angles (Table 1) show that the N11ÐC11 bond almost eclipses the C12ÐH12A bond; the C11ÐN11ÐC12ÐH12A angle is only 2.3  . The two halves of the molecule are otherwise each nearly planar. The bond lengths and interbond angles agree closely with those found by Sun et al. (2004) and show no unusual values. The molecules of (I) are linked into sheets by a single, fairly short, CÐHO hydrogen bond (Table 2). Atoms C6 at (x, y, z) and (1  x,1  y 1  z), which lie in the molecule centred at ( 1 2 , 1 2 , 1 2 ), act as hydrogen-bond donors, respectively, to atoms O41 at ( 1 2 + x, 3 2  y,  1 2 + z) and ( 3 2  x,  1 2 + y, 3 2  z), which themselves lie in the molecules centred at (0, 1, 0) and (1, 0, 1). In a similar way, atoms O41 at (x, y, z) and (1  x,1  y, 1  z) accept hydrogen bonds from atoms C6 at ( 1 2 + x, 3 2  y, 1 2 + z) and ( 1 2  x,  1 2 + y, 1 2  z), respectively, which lie in the organic compounds Acta Cryst. (2005). C61, o53±o56 DOI: 10.1107/S0108270104030719 # 2005 International Union of Crystallography o53 Acta Crystallographica Section C Crystal Structure Communications ISSN 0108-2701 Figure 1 The molecule of (I), showing the atom-labelling scheme. Atoms labelled with the suf®x `A' are at the symmetry position (1  x,1  y,1  z), and displacement ellipsoids are drawn at the 30% probability level.