1-[(E)-2-Formyl-1-(4-methylphenyl)- ethenyl]-3-(4-methylphenyl)pyrazole-4- carbaldehyde P. Ramesh, a A. Subbiahpandi, a Ramaiyan Manikannan, b S. Muthusubramanian b and M. N. Ponnuswamy c * a Department of Physics, Presidency College (Autonomous), Chennai 600 005, India, b Department of Organic Chemistry, School of Chemistry, Madurai Kamaraj University, Madurai 625 021, India, and c Centre of Advanced Study in Crystallography and Biophysics, University of Madras, Guindy Campus, Chennai 600 025, India Correspondence e-mail: mnpsy2004@yahoo.com Received 20 August 2008; accepted 28 August 2008 Key indicators: single-crystal X-ray study; T = 293 K; mean (C–C) = 0.002 A ˚ ; R factor = 0.055; wR factor = 0.174; data-to-parameter ratio = 26.4. In the crystal structure of the title compound, C 21 H 18 N 2 O 2 , molecules are linked through C—HO interactions. Two symmetry-related molecules form a cyclic centrosymmetric R 2 2 (20) dimer. These dimers are further connected into chains running along the b axis. Related literature For related literature, see: Baraldi et al. (1998); Bernstein et al. (1995); Bruno et al. (1990); Chen & Li (1998); Cottineau et al. (2002); Londershausen (1996); Mishra et al. (1998); Smith et al. (2001). Experimental Crystal data C 21 H 18 N 2 O 2 M r = 330.37 Monoclinic, P2 1 =n a = 10.2914 (4) A ˚ b = 15.3618 (5) A ˚ c = 11.0271 (4) A ˚  = 98.778 (1)  V = 1722.90 (11) A ˚ 3 Z =4 Mo K radiation  = 0.08 mm 1 T = 293 (2) K 0.30  0.20  0.16 mm Data collection Bruker APEXII CCD area-detector diffractometer Absorption correction: multi-scan (SADABS; Sheldrick, 2001) T min = 0.980, T max = 0.987 24747 measured reflections 6019 independent reflections 3731 reflections with I >2(I) R int = 0.025 Refinement R[F 2 >2(F 2 )] = 0.055 wR(F 2 ) = 0.174 S = 1.04 6019 reflections 228 parameters H-atom parameters constrained Á max = 0.35 e A ˚ 3 Á min = 0.30 e A ˚ 3 Table 1 Hydrogen-bond geometry (A ˚ ,  ). D—HA D—H HA DA D—HA C22—H22AO2 i 0.96 2.60 3.378 (2) 139 C5—H5O1 ii 0.93 2.23 3.1094 (17) 159 Symmetry codes: (i) x þ 3; y; z; (ii) x þ 3 2 ; y  1 2 ; z þ 1 2 . Data collection: APEX2 (Bruker, 2004); cell refinement: APEX2; data reduction: SAINT (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2003). PR thanks Dr Babu Varghese, SAIF, IIT, Madras, India, for his help with the data collection. Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BT2774). References Baraldi, P. G., Manfredini, S., Romagnoli, R., Stevanato, L., Zaid, A. N. & Manservigi, R. (1998). Nucleosides Nucleotides, 17, 2165–2171. Bernstein, J., Davis, R. E., Shimoni, L. & Chang,N. L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555–1573. Bruker (2004). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Bruno, O., Bondavalli, F., Ranise, A., Schenone, P., Losasso, C., Cilenti, L., Matera, C. & Marmo, E. (1990). Farmaco, 45, 147–66. Chen, H. S. & Li, Z. M. (1998). Chem. J. Chin. Univ. 19, 572–576. Cottineau, B., Toto, P., Marot, C., Pipaud, A. & Chenault, J. (2002). Bioorg. Med. Chem. 12, 2105–2108. Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565. Londershausen, M. (1996). Pestic. Sci. 48, 269–274. Mishra, P. D., Wahidullah, S. & Kamat, S. Y. (1998). Indian J. Chem. Sect. B, 37, 199. Sheldrick, G. M. (2001). SADABS. University of Go ¨ttingen, Germany. Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Smith, S. R., Denhardt, G. & Terminelli, C. (2001). Eur. J. Pharmacol. 432, 107–119. Spek, A. L. (2003). J. Appl. Cryst. 36, 7–13. organic compounds Acta Cryst. (2008). E64, o1889 doi:10.1107/S1600536808027694 Ramesh et al. o1889 Acta Crystallographica Section E Structure Reports Online ISSN 1600-5368