| Abstract: | The crystal of ES-1 belongs to the orthorhombic system, space group Pbca. Unit cell parameters were determined by least squares method and found to be: a = 16.256(8), b = 15.359(8), and c = 9.918(5) Å. The structure was solved by direct methods using the program SHELX86. The refinement was carried out using isotropic thermal parameters then followed by several cycles of anisotropic least squares to a final value of R0 = 0.073 for 1226 observed reflections. The hydrogen atoms were located from a difference Fourier map. Torsion angles calculation showed that rings A and B are planar as expected. All the calculations were carried out on a PC-Computer at physics department, Tanta University. |
