Estudos estruturais de pequenas e médias moléculas por difração de raios-x em monocristais

Abstract

Five compounds, three organic and two organometallic, were studied by x-ray diffraction in single crystals and their structure was successfully determined in four of five compounds. The measurements were made in diverse equipments, depending on the availability, providing data sets of different quality levels. The structure of the compound C8H10O2N3 (SAS) was solved by direct methods. The SAS crystallizes with monoclinic symmetry, space group C 2/c (Z=8) and lattice parameters a = 13.225(3), b = 5.271(1), c = 24.919(5), = 104.12(3). The good quality of the data allowed the refinement to achieve a residual index Robs = 0.040 (F2 2), considered very acceptable. The second studied compound is a bimetallic complex of cupper and furoic acids. The structure was successfully solved, through the heavy atom method and subsequent Fourier difference analysis. The compound crystallizes in the space group P21 with 4 units of Cu2(O2CC4H3O)4(H2O)2 .2H2O per unit cell. The lattice parameters are a = 13.225(3), b = 5.271(1), c = 24.919(5) e = 104.12(3). The refinement achieved a residual index Robs = 0.066. The resolution limit of the data set associated to the occupational disorder of the water molecules prevented further convergence. The structure of the small molecule N(4)-phenyl-2-benzoylpyridine thiosemicarbazone (C19H16N4S) was successfully solved via direct methods, despite the low resolution of the data set. The refinement converged with the C 2/m (Z=8) space group and lattice parameters a = 17.8336(7) Å, b = 9.1202(9) Å, c = 21.864(1) Å e = 105.286(9) º. A residual index of Robs = 0.040 was achieved. Following the above work, a metallic complex between tin and the C19H16N4S thiosemicarbazone was crystallized. The structure determination converged to space group Pn with 4 units of SnCl(C19H16N4S)(C4H9)2 per unit cell. The lattice parameters area = 9.8353(5) Å, b = 23.898(1) Å, c = 12.421(5) Å e = 105.286(9) º. The refinement achieved a residual index Robs = 0.037, due to the good quality of the data set. The organic compound -CD:TMDP can be characterized as a medium molecule, containing 208 atoms in the asymmetric unit and a total of 832 atoms in the unit cell. Due to the limitations of the equipment used, only 1800 unique reflections were collected. The -cyclodextrin molecule was located by molecular replacement technique, but the structure determination could not be completed with success. Crystallization happened in the C 2/m space group (Z=4) with lattice parameters a = 19.447(4) Å, b = 24.145(5) Å, c = 16.895(4) Å e = 103.75(3)º. These results were obtained by the precession technique and confirmed by the measurements made on LNLS.