RESUMO
This study is an investigation into the crystal structure of the biologically active drug mol-ecule riluzole [RZ, 6-(tri-fluoro-meth-oxy)-1,3-benzo-thia-zol-2-amine], C8H5F3N2OS, and its derivative, the riluzolium chloride salt [RZHCl, 2-amino-6-(tri-fluoro-meth-oxy)-1,3-benzo-thia-zol-3-ium chloride], C8H6F3N2OS+·Cl-. In spite of repeated efforts to crystallize the drug, its crystal structure has not been reported to date, hence the current study provides a method for obtaining crystals of both riluzole and its corresponding salt, riluzolium hydro-chloride. The salt was obtained by grinding HCl with the drug and crystallizing the obtained solid from di-chloro-methane. The crystals of riluzole were obtained in the presence of l-glutamic acid and d-glutamic acid in separate experiments. In the crystal structure of RZHCl, the -OCF3 moiety is perpendicular to the mol-ecular plane containing the riluzolium ion, as can be seen by the torsion angle of 107.4â (3)°. In the case of riluzole, the torsion angles of the four different mol-ecules in the asymmetric unit show that in three cases the tri-fluoro-meth-oxy group is perpendicular to the riluzole mol-ecular plane and only in one mol-ecule does the -OCF3 group lie in the same mol-ecular plane. The crystal structure of riluzole primarily consists of strong N-Hâ¯N hydrogen bonds along with weak C-Hâ¯F, C-Hâ¯S, Fâ¯F, Câ¯C and Câ¯S inter-actions, while that of its salt is stabilized by strong [N-H]+â¯Cl- and weak C-Hâ¯Cl-, N-Hâ¯S, C-Hâ¯F, Câ¯C, Sâ¯N and Sâ¯Cl- inter-actions.