I. INTRODUCTION
3-Amino-5-(aminocarbonyl)-2,4,6-triiodobenzoic acid is currently used as a precursor of iosimenol, a non-ionic radiocontrast agent with both low osmolality and viscosity and good water solubility (Sovak et al., Reference Sovak, Terry, Abramjuk, Faberová, Fiserova, Laznicek, Leuschner, Malinak, Zahradnik, Masner and Seligson2004; Bailey et al., Reference Bailey, Jones, Kneller, Petrov, White, Egan and Rooney2013). In order to produce iosimenol in commercial quantities, its manufacture process must be economic. Such process requires efficient purification techniques, for assuring high yields and high purities in each synthetic step. However, the use of such techniques needs to be cost-effective, and crystallization seems to be the best method. In this manner, the structure of single iosimenol precursors and accompanying impurities is seeked in order to design superior purification techniques. Thus, we present data for the title compound crystallizing as a methanol solvate, as shown in Figure 1.
Figure 1. Structural formula of 3-amino-5-(aminocarbonyl)-2,4,6-triiodobenzoic acid methanol solvate.
We have inspected the CSD database (Allen, Reference Allen2002) and the PDF4+ database (ICDD, 2015) and have not found any entry for this organic substance C9H9I3N2O4 in the mentioned databases. Therefore, we have decided to characterize this compound by X-ray powder diffraction (XRD) technique.
II. EXPERIMENTAL
A. Synthesis
The title compound was prepared by reacting 3-amino-5-(aminocarbonyl) benzoic acid and sodium iodine dichloride or iodine monochloride in an aqueous solvent, under acidic conditions, at a temperature of 65–85 °C. The crude product was then recrystallized twice from a refluxing mixture of methanol/water.
B. Density measurement
For the title compound, experimental density was evaluated as an average of 10 measurements in 50 ml pycnometer, using n-heptane as a liquid, resulting in a value of ρ m = 2.66(3) g cm−3.
C. Specimen preparation
Sample was prepared by careful grinding in an agate mortar and front-loaded into the specimen holder.
D. Diffraction data collection and reduction
The diffraction pattern for the title compound was collected at room temperature with an X'Pert3 Powder θ–θ powder diffractometer with parafocusing Bragg-Brentano geometry using CuKα radiation (λ = 1.5418 Å, Ni filter, generator setting: 40 kV, 30 mA). An ultrafast PIXCEL detector was employed to collect XRD data over the angular range from 5° to 80°2θ with a step size of 0.013°2θ and a counting time of 118.32 s step−1.
The software package HighScore Plus V 3.0e (PANalytical, Almelo, The Netherlands) was used to smooth the data, to fit the background, to eliminate the K α 2 component and the top of the smoothed peaks were used to determine the peak positions and intensities of the diffraction peaks (Table I). The d-values were calculated using CuK α 1 radiation (λ = 1.5406 Å).
TABLE I. Indexed X-ray powder diffraction data for C9H9I3N2O4. Only the peaks with I rel of 1 or greater are presented [a = 17.000 (1) Å, b = 13.896 (1) Å, c = 12.597 (1) Å, unit-cell volume V = 2975.9 Å3, Z = 8, space group Pbca]. All lines were indexed and are consistent with the Pbca space group. The d-values were calculated using CuKα 1 radiation (λ = 1.5406 Å).
III. RESULTS AND DISCUSSION
The experimental powder diffraction pattern is depicted in Figure 2. Automatic indexing of results obtained using DICVOL04 (Boultif and Louër, Reference Boultif and Louër2004) show that title compound C9H9I3N2O4 is orthorombic with space group Pbca and unit-cell parameters: a = 17.000 (1) Å, b = 13.896 (1) Å, c = 12.597 (1) Å, unit-cell volume V = 2975.9 Å3, and Z = 8. The figures of merits are F 20 = 70.5(0.0053, 53) (Smith and Snyder, Reference Smith and Snyder1979), and M 20 = 28.7 (de Wolff, Reference de Wolff1968). All measured lines were indexed and are consistent with the Pbca space group.
Figure 2. (Color online) X-ray powder diffraction pattern of C9H9I3N2O4 using CuK α radiation (λ = 1.5418 Å).
SUPPLEMENTARY MATERIAL
The supplementary material for this article can be found at https://doi.org/10.1017/S0885715617000598.
ACKNOWLEDGEMENTS
This work was carried out within the framework of the National Programme for Sustainability (NPU I LO1215) Ministry – 34870/2013), GACR project 16-25747S and specific university research (MSMT No 20-SVV/2016).
