Análise estrutural de duas nitro azinas assimétricas

Abstract

Azines are compounds derived from hydrazones, both of them are used in various biological applications such as antioxidant, antitumor, acetylcholinesterase activity, among others. The general structure of azines is defined by the presence of two aromatic rings and one azomethine group. Crystallographic methodology allows the identification of all the atoms that make up the map of electron density of molecules in the crystalline solid state. The general fundamentals of crystallography are symmetry, X-ray diffraction and electron density. This work briefly described these theoretical concepts and all experimental stages that make up this methodology. The objective of this study was the structural elucidation of asymmetric azines (7E,8E)-2-(3-methoxy- 4-hydroxy-benzylidene)-1-(4-nitrobenzylidene)-hydrazine and (7E,8E)-1-(4- nitrobenzylidene)-2-(4-Dimethylamino-benzylidene)-hydrazine using crystallographic methodology of single crystal X-ray diffraction. In the crystallization step utilized the direct method, with the slow evaporation of the dichloromethane solvent. The C15H13N3O4 and C16H16N4O2 azines crystallized in space group P21/n and P1̅ respectively. The solutions of the structures were performed by Methods Direct and refinement by Least Squares technique. In the analysis of the structure the molecules were evaluated their intramolecular parameters such as geometry, intramolecular interactions, planarity and substituents, while the intermolecular parameters was described the interactions of the non classical hydrogen bonds CH...O, CH...π, classical hydrogen bonds O-H...O, unconventional interactions C-H...H-C and interactions π…π that contributed in the crystalline supramolecular arrangement. The two asymmetric azines are planar and have similar geometric factors. The difference between both is verified structurally, by the substituents of the aromatic rings and according to the chemical environments of intermolecular interactions. In particular, the azine C16H16N4O2, there is evidence that the loss occurred apparent symmetry in the structure due to the existence of another element of symmetry beyond the center of inversion.