organic papers Acta Cryst. (2005). E61, o49±o51 doi:10.1107/S1600536804031927 Low et al.  C 22 H 24 ClN 3 O o49 Acta Crystallographica Section E Structure Reports Online ISSN 1600-5368 3-tert-Butyl-1-(4-chlorophenyl)-7,7-dimethyl-5,6,7,8- tetrahydropyrazolo[3,4-b]quinolin-5-one: centro- symmetric dimers generated by CÐHp(arene) hydrogen bonds John N. Low, a *³ Justo Cobo, b Jaime Mera, c Jairo Quiroga c and Christopher Glidewell d a Department of Chemistry, University of Aberdeen, Meston Walk, Old Aberdeen AB24 3UE, Scotland, b Departamento de Quõ Âmica Inorga Ânica y Orga Ânica, Universidad de Jae Ân, 23071 Jae Ân, Spain, c Grupo de Investigacio Ân de Compuestos Heterociclõ Âcos, Departamento de Quõ Âmica, Universidad de Valle, AA 25360 Cali, Colombia, and d School of Chemistry, University of St Andrews, Fife KY16 9ST, Scotland ³ Correspondance address: Department of Electrical Engineering and Physics, School of Engineering and Physical Science, University of Dundee, Dundee DD1 4HN, Scotland. Correspondence e-mail: che562@abdn.ac.uk Key indicators Single-crystal X-ray study T = 293 K Mean (C±C) = 0.004 A Ê R factor = 0.053 wR factor = 0.122 Data-to-parameter ratio = 17.2 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 Molecules of the title compound, C 22 H 24 ClN 3 O, are linked by two pairs of CÐH(arene) hydrogen bonds into centro- symmetric dimers. Comment We report here the structure of the title compound, (I) (Fig. 1), whose supramolecular aggregation shows some interesting differences from that in the unsubstituted analogue (II) (Low et al., 2004). The bond lengths in (I) are very similar to those in (II) and require no further discussion here. The ring-puckering para- meters (Cremer & Pople, 1975) for the carbocyclic rings in (I) and (II) are quite similar [for the atom sequence C4AÐC5Ð Received 30 November 2004 Accepted 2 December 2004 Online 11 December 2004 Figure 1 The molecule of compound (I), showing the atom labelling scheme. Displacement ellipsoids are drawn at the 30% probability level.