Crystal structure and characterization of L-arginine chlorate and L-arginine bromate * A.M. Petrosyan a, * , H.A. Karapetyan a , R.P. Sukiasyan a , A.E. Aghajanyan b , V.G. Morgunov c , E.A. Kravchenko c , A.A. Bush d a Molecule Structure Research Center, NAS, 26 Azatutyan Ave., Yerevan 375014, Armenia b Institute of Biotechnology, 14 Gyurjyan St., Yerevan 375056, Armenia c Institute of General and Inorganic Chemistry, RAS, 31 Leninskii pr., Moscow 123812, Russia d Moscow State Institute of Radioengineering, Electronics and Automation, 78 Vernadskii St., Moscow 119454, Russia Received 17 January 2005; revised 25 May 2005; accepted 25 May 2005 Available online 20 July 2005 Abstract The salts L-arginine.HClO 3 and L-arginine.HBrO 3 , were synthesized. The crystals obtained were characterized by IR and NQR spectroscopy, thermal analysis, Nd:YAG laser radiation second harmonic generation, dielectric, piezoelectric and pyroelectric measurements and their crystal structures were determined. L-arginine.HClO 3 and L-arginine.HBrO 3 are crystallized in orthorhombic (space group P2 1 2 1 2 1 ) and triclinic (space group P1) systems, respectively. Their structures consist of the protonated arginine cation [ C (H 2 N) 2 CNH(CH 2 ) 3- CH(NH 3 C )COO K ] and respective ClO 3 K or BrO 3 K anions. Hydrogen bonds (stronger in the bromate) connect anions with cations and the latter with each other. However, these salts have essential distinctions in crystal packing. q 2005 Elsevier B.V. All rights reserved. Keywords: L-Arginine chlorate; Bromate; Crystal structure; Solution growth; Properties 1. Introduction L-Arginine phosphate monohydrate L-Arg.H 3 PO 4 .H 2 O (LAP) is one of the best nonlinear optical crystals [1]. However, growth of the LAP crystals has attendant growth of microorganisms, which can be detrimental to crystal quality. Hence, the preparation procedure requires special precautions. It has been suggested that the appearance of microorganisms can be prevented by either adding H 2 O 2 [2] or Hg [3] into solution or by covering the solution with a layer of n-hexane [4]. Ongoing investigations [5–9], however, showed that this does not completely solve the problem. Search for new members of the LAP family may produce crystals, whose parameters can surpass those of the LAP. In addition, the preparation of such crystals may be free of the problem of microorganisms [10–13]. Systematic search for new LAP-analogs was started by Monaco et al. [14], who investigated some previously known and a number of new crystals. The interaction of L-arginine with iodic acid only, among the halogenic acids HClO 3 , HBrO 3 , HIO 3 , was investigated to give powdered L-Arg.HIO 3 . The weak broad iodine-127 lines were observed in the nuclear quadrupole resonance (NQR) spectrum [15], which to a certain extent, was evidence for the crystallinity of the compound. In addition, it was found that L-Arg.2HIO 3 comprising a doubly charged arginine cation [ C (H 2 N) 2- CNH(CH 2 ) 3 CH(NH 3 C )COOH] exists, which, in contrast to L-Arg.HIO 3 crystallizes easily [15]. In this respect, we found it interesting to study the possibility of formation and crystallization of the respective salts of L-arginine with chloric (HClO 3 ) and bromic (HBrO 3 ) acids. 2. Experimental As initial compounds, we used L-arginine, synthesized in the Institute of Biotechnology (Yerevan), and a reagent Journal of Molecular Structure 752 (2005) 144–152 www.elsevier.com/locate/molstruc 0022-2860/$ - see front matter q 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.molstruc.2005.05.053 * CCDC 259335 and CCDC 259336 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: C44 1223 336033). * Corresponding author. Tel.: C374 1 281764; fax: C374 1 282267. E-mail address: apetros@msrc.am (A.M. Petrosyan).