0022-4766/13/5403-0619 © 2013 Springer Science+Business Media, Inc. 619 Journal of Structural Chemistry. Vol. 54, No. 3, pp. 619-623, 2013 Original Russian Text Copyright © 2013 by L. D. Popov, S. I. Levchenkov, I. N. Shcherbakov, G. G. Aleksandrov, Yu. P. Tupolova, V. V. Lukov, O. I. Askalepova, V. A. Kogan CRYSTAL STRUCTURE OF THE POLYCYCLIC OXIDATION PRODUCT OF 1′-PHTHALAZINYLHYDRAZONE OF 2-FORMYLPYRROLE L. D. Popov, 1 S. I. Levchenkov, 2 I. N. Shcherbakov, 1 G. G. Aleksandrov, 3 Yu. P. Tupolova, 1 V. V. Lukov, 1 O. I. Askalepova, 1 and V. A. Kogan 1 UDC 539.27:544.18:547.556.93 Phthalazinylhydrazone of 2-formylpyrrole is synthesized, the values of ionization constants are determined, and quantum chemical calculation of the geometry and total energy of possible tautomers is performed. The structure of the cyclic oxidation product of hydrazone 3-(1H-pyrrolyl-2)-[1,2,4]-triazolo(3,4-a)phthalazine existing in the crystal in the form of dimers linked by two hydrogen bonds is described. DOI: 10.1134/S0022476613030232 Keywords: hydrazones, single crystal X-ray diffraction analysis, hydrogen bond, density functional theory. Hydrazones based on 1-hydrazinophthalazine (hydralazine) have been actively studied due to biological activity displayed by these compounds, primarily hypotensive and anti-inflammatory [1-4]. The investigation of these compounds is stimulated by the fact that the metabolism of hydralazine implies its interaction with carbonyl compounds forming in the Krebs cycle [5-7] and high complexing ability of phthalazinylhydrazones [8]. In the literature, a wide range of hydralazine hydrazones with different mono- and dicarbonyl compounds [8-16] is described. This work presents the results of the synthesis, physical chemical study, and quantum chemical simulation of 1′-phthalazinylhydrazone of pyrrole-2-aldehyde. EXPERIMENTAL Phthalazinylhydrazone of pyrrole-2-aldehyde (1) was synthesized as follows. Equimolar amounts of pyrrole-2- aldehyde, 1-hydrazinophthalizine hydrochloride, and sodium acetate were boiled in 30 ml of ethanol for 5 h, then 50 ml of water were added. The yellow precipitate was filtered off and washed with water and ethanol. Recrystallized from methanol. Yield 65%. Т m 214°C. Elemental analysis: chemical formula C 13 H 11 N 5 ; calculated (%): C 65.8, H 4.67, N 29.5; found (%): C 66.2, H 459, N 28.9. The IR spectrum (KBr, ν, cm –1 ): 3199, 3162 (NH), 1610, 1572 (C=N). The 1 Н NMR (DMSO-d 6 , δ, ppm, J, Hz): 11.88 (s, 1H, NH); 10.37 (s, 1H, NH); 8.08 (s, 1H, CH azomethine ); 8.23 (d, 1H, J = 6.6, CH phthalazine ); 784 (s, 1H, CH phthalazine ); 7.55-764 (m, 3H, CH phthalazine ); 6.87 (d, 1H, J = 3.0, CH pyrrole ); 6.07-6.23 (m, 2H, CH pyrrole ). 1 Faculty of Chemistry, Southern Federal University, Rostov-on-Don. 2 Southern Scientific Center, Russian Academy of Sciences, Rostov-on-Don. 3 N. S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Moscow; physchem@yandex.ru. Translated from Zhurnal Strukturnoi Khimii, Vol. 54, No. 3, pp. 565-569, May-June, 2013. Original article submitted May 30, 2012.