Radiation damage produced in single crystal of iminodiacetic acid hydrobromide Murat Aydin a, * ,S ßemsettin Osmanog ˘lu b , M. Halim Bas ßkan c , I. Yes ßim Dicle d a Faculty of Education, Adıyaman University, TR 02030 Adıyaman, Turkey b Faculty of Education, Siirt University, Turkey c Faculty of Education, Dicle University, Diyarbakir, Turkey d Faculty of Arts and Sciences, Dicle University, Diyarbakir, Turkey article info Article history: Received 13 November 2009 Received in revised form 26 March 2010 Accepted 26 March 2010 Available online 2 April 2010 Keywords: EPR Free radicals Iminodiacetic acid derivatives Gamma irradiation abstract Single crystals of iminodiacetic acid hydrobromide, H 2 N(CH 2 COOH) 2 Br, were gamma-irradiated and the formed paramagnetic species were investigated at room temperature and analyzed for different orienta- tions of the crystal in the magnetic field by electron paramagnetic resonance technique. The observed species in iminodiacetic acid hydrobromide single crystals were attributed to the H 2 NC ˙ HCH 2 (COOH) 2 Br radical. The g values and hyperfine coupling constants of the unpaired electron with the environmental a-proton, methylene protons, and one proton of the NH 2 , and 14 N nucleus were determined. The results were found to be in good agreement with the existing literature data. Ó 2010 Elsevier B.V. All rights reserved. 1. Introduction Free radicals are chemical species that possess an unpaired electron in the outer shell of the molecule. Free radicals are formed mainly in case of irradiation of solid. For irradiated solids, they can be generated by homolytic cleavage of a covalent bond, in which a normal molecule fragments into two, each fragment retaining one of the paired electrons. Due to the fact that unpaired electron is in- volved in free radicals, these species are paramagnetic and the most used method for detecting free radicals is electron paramag- netic resonance (EPR) technique [1]. Investigations on spectro- scopic splitting factor (g values) and proton hyperfine splittings give valuable information on the electronic structure of paramag- netic centers [2]. The EPR technique has been widely used in the identification of irradiation damage centres in many substances, including amino acids and iminodiacetic acid derivatives [3–11]. Gamma-irradiated single crystals of iminodiacetic acid were inves- tigated at room temperature by EPR [12]. The radiation damage center was attributed to the HNC ˙ HCH 2 (COOH) 2 radical. Further- more, powders of iminodiacetic acid and methyliminodiacetic acid were gamma-irradiated and studied at room temperature with EPR technique [13]. Iminodiacetic acid is a biologically important material [12]. It is particularly effective in inhibiting formation and deposition of cal- cium and barium scales in aqueous systems, such as cooling water systems [14]. General interest to physics and chemistry of amine radicals can be understood by the close relation to the amine group –NH 2 , which highly abundant in organic chemistry as a functional group that affects molecular reactivity. Therefore the aim of this work is to investigate the defects induced by gamma irradiation in single crystals of iminodiacetic acid hydrobromide (IDAHBr) and to determine their spin Hamiltonian parameters at room temperature. 2. Experimental Single crystals of IDAHBr were grown from concentrated aque- ous solutions by slow evaporation. Crystallography of single crys- tals of IDAHBr has been studied [15]. It is orthorhombic, with space group Pmmn and has two molecules in a unit cell. The unit cell dimensions are a = 12.815, b = 5.871, and c = 5.087 Å. The crys- tals were irradiated at room temperature with a 60 Co c-ray source of 40 kGy. Room temperature spectra were recorded using a Varian model X-band E-109C EPR spectrometer. The magnetic field mod- ulation frequency was 100 kHz. The crystals were mounted on a goniometer and the spectra were recorded in three mutually per- pendicular planes by rotating the crystal around the a, b and c crys- tallographic axes at 10° intervals. The g values were found by comparison with a dipenhylpicrylhydrazyl (DPPH) sample of g = 2.0036. The gamma-irradiated samples were stored at room temperature before recording the EPR spectra, and after the mea- surements the spectra were checked for several months to follow the stability of the formed species. The simulation of the spectra using the EPR similation program of McKelvey [16], are shown in Figs. 1b–3b. 0022-2860/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.molstruc.2010.03.073 * Corresponding author. Tel.: +90 416 2232210; fax: +90 416 2231426. E-mail address: maydin@adiyaman.edu.tr (M. Aydin). Journal of Molecular Structure 975 (2010) 30–32 Contents lists available at ScienceDirect Journal of Molecular Structure journal homepage: www.elsevier.com/locate/molstruc