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The subject of the present study is L-arginine dichloride (L–Arg·2HCl) crystal. The thermal properties, vibrational spectra and second harmonic generation activity were studied. The crystal and molecular structure of L–Arg·2HCl crystal was determined by the single-crystal X-ray diffraction method at 295K. This crystallize in the monoclinic (P21) system. Unit cell parameters: a=7.4907(15) Å, b=20.092(4) Å, c=12.101(2) Å, α=γ=90˚, β=99.35(3)˚, Z=6, Dc=1.370 g/cm3, V=1797.0(6)Å3. The asymmetric part of the unit cell of L–Arg·2HCl contains crystallographically independent three L-argininium (2+) cations and six Cl- anions (3L-Arg2+·6Cl-). The layers of arginine cations are formed in the bc plane, and these layers are connected through Cl- anions, forming strong hydrogen bonds. In [1] were divided the interactions of the guanidyl group with carboxylate and phosphate anions into four types, and only one of the 25 studied compounds were encountered a Type D interaction. In the L-Arg·2HCl structure, the interaction between the anion and the guanidyl group is very similar to the Type D. The bulk crystals were grown. They exhibit nonlinear optical properties.
1. Salunke, D. M. & Vijayan M. (1981), Int. J. Peptide Protein Res. 18, 348.
Acknowledgments: The research was supported by the Higher Education and Science Committee of MESCS RA (Research project № 24WS-1C022).