Crystal structure of a unique sodium distorted linkage in diclofenac sodium pentahydrate.

a sodium salt of 2-[(2,6-dichlorophenyl)amino]benzeneacetic acid, is an important non-steroid anti-inflammatory drug used in rheumatology. 1 In this paper we present the crystal structure of diclofenac sodium pentahydrate (C14H10Cl2NO2) – Na + ·5H2O along with its unique sodium distorted linkage, which were recrystallized from a matrix of chitosan and diclofenac sodium. Ethyl acetate was added to a mixture solution of chitosan and diclofenac sodium in aqueous acetic acid. Then, suitable single crystals of diclofenac sodium pentahydrate were recrystallized from the mixture solution by slow evaporation. X-ray diffraction data were collected at room temperature using a Bruker SMART CCD area detector. The collected data were reduced using SAINT, 2 and an empirical absorption correction was performed using SADABS. 3 A total of 18248 reflections were measured, of which 6250 reflections (R(int) = 0.0268) were unique. The structure was solved by direct methods and refined with anisotropic displacement parameters for all non-hydrogen atoms by full-matrix least-squares using the SHELX-97 package for PC. 4 The O2, O12 and Na4 were refined disordered. The coordinates of the hydrogen atoms were calculated from the riding model, except for hydrogen atoms connected to diclofenac molecules. They were found from difference Fourier maps, and were included in a refinement with isotropic displacement parameters. The crystal and experimental data are given in Table 1. The atomic parameters for non-hydrogen atoms are listed in Table 2. An ORTEP 5 drawing of the discrete diclofenac anions in an asymmetric unit with atomic labeling is shown in Fig 1. The repeating unit of the distorted Na linkage is shown in Fig. 2. The crystal has two independent diclofenac molecules in the asymmetric unit. The bond distances and angles within the diclofenac anions are within the expected ranges; and also, both molecules are similar in terms of their bond lengths and angles. The crystal structure of diclofenac sodium forms polymeric units of (C14H10Cl2NO2) – Na + ·5H2O. The sodium linkages stretch along the a-axis located at the 1/4b-axis and 3/4b-axis (Fig. 3). It is interesting that the sodium infinite chains are built from a distorted Na(H2O)6 octahedral unit. An asymmetric unit of the sodium linkage consists of four Na(H2O)6 distorted octahedral units. Three of them are built as a polymeric chain and the other Na unit is bridged between the two Na octahedral units with point sharing as a trimeric unit. The Na3 octahedral links to the Na1 octahedral unit with face …