Sarcosine sarcosinium chloride and sarcosine sarcosinium bromide V.V. Ghazaryan a , M. Fleck b , A.M. Petrosyan a,⇑ a Institute of Applied Problems of Physics, NAS of Armenia, 25 Nersessyan Str., 0014 Yerevan, Armenia b Institute of Mineralogy and Crystallography, University of Vienna, Althanstr. 14, A-1090 Vienna, Austria article info Article history: Received 10 March 2012 Accepted 3 April 2012 Available online 11 April 2012 Keywords: Sarcosine salts Dimeric cation Crystal structure Vibrational spectra abstract The crystal and molecular structures and vibrational spectra of sarcosine sarcosinium chloride (I) and sar- cosine sarcosinium bromide (II) have been determined and are discussed. In the case of sarcosine sarcos- inium bromide (II), an old publication exists, where the structure is reported, but the data given are less accurate and hydrogen positions have not been determined at all. Both salts are isotypic and crystallize in the orthorhombic system (space group Pca2 1 ), the asymmetric unit contains two formula units. The OO distances in dimeric cations are equal to 2.469(2) Å and 2.463(2) Å in (I) and 2.453(3) Å and 2.464(3) Å in (II). The presence of these short hydrogen bonds is reflected in the infrared spectra. The vibrational spec- tra of sarcosinium chloride and sarcosinium bromide are shown for comparison. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction Salts of amino acids with an (AA + ) type dimeric cation, where A and A + are amino acids in zwitterionic and singly charged amino acids, represent an interesting class of materials from different points of view, i.e. as species with very short hydrogen bonds, crys- tals in which phase transitions are possible, and additionally, many of them as promising candidates for nonlinear optical materials. Recently [1] we reported our preliminary results on 20 new salts with dimeric cation in addition to ca. 40 previously known such salts (see respective references in [1]). In [1] we showed a histo- gram of all known OO distances, the shortest value being 2.414 Å (in 2L-ProHNO 3 [2] and in 2L-AlaHCl [1]), the longest equals 2.564 Å (in 2GlyHBr [3]). We mentioned also that in the literature there is an even smaller value, viz. 2.40 Å, for the OO distance in one of two dimers in the structure of disarcosine hydro- bromide [4]. However, we noted that this value has to be regarded critically since the structural data are not of high accuracy (R = 0.11) and no root-mean-square error is provided. The second known salt of sarcosine with 2:1 composition and dimeric cation is sarcosine sarcosinium methanesulfonate [5,6]. In continuation of our work in this direction (recently we sub- mitted papers on L-alanine L-alaninium picrate monohydrate [7] and sarcosine sarcosinium tetrafluoroborate and perchlorate [8]), here we present our results on the structure determination of sar- cosine sarcosinium chloride and the structure redetermination of sarcosine sarcosinium bromide. Moreover, we present and discuss the infrared and Raman spectra of these crystals, and also those of sarcosinium chloride and sarcosinium bromide for comparison. The structure of sarcosinium chloride has been determined previ- ously [9]. 2. Experimental procedure 2.1. Synthesis and crystal growth As initial reagents we used sarcosine purchased from ‘‘Sigma’’ and hydrochloric, hydrobromic acids of ‘‘chemically pure’’ and ‘‘special pure’’ grade (‘‘Reakhim’’), which were 32% and 40.5% solu- tions respectively. The crystals 2SarHCl and 2SarHBr have been obtained by slow evaporation at room temperature from aqueous solution containing stoichiometric ratios of respective components. Crystals of SarHCl and SarHBr have been obtained from solution containing 1:1.3 M ratio of respective components. At stoichiome- tric 1:1 ratio a mixture of 2.1 and 1.1 compounds is formed. 2.2. Crystal structure determination and refinement Single-crystal X-ray intensity data of the title compounds were collected at 296 K on an Bruker-Nonius APEX II diffractometer, equipped with a CCD area detector and employing graphite-mono- chromated Mo Ka radiation (k = 0.71073 Å). For the measurement, suitable single crystals sample of the title compounds with sizes of approximately 0.8  0.4  0.4 mm 3 were mounted on a thin glass needle with laboratory grease. For both species, a full Ewald sphere was measured. The reflection data were collected and processed using the Bruker-Nonius program suites COLLECT, DENZO-SMN and related analysis software [10,11]. The structures were solved by direct methods and subsequent Fourier and difference Fourier 0022-2860/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.molstruc.2012.04.008 ⇑ Corresponding author. Tel.: +374 10 241106; fax: +374 10 281861. E-mail addresses: aram.m.petrosyan@gmail.com, apetros@iapp.sci.am (A.M. Petrosyan). Journal of Molecular Structure 1020 (2012) 160–166 Contents lists available at SciVerse ScienceDirect Journal of Molecular Structure journal homepage: www.elsevier.com/locate/molstruc