Síntese, caracterização, estudo fatorial e atividade antimicrobiana de complexos binucleares de cromo(III) contendo ligantes tripédicos

Abstract

Building blocks are widely used within chemical synthesis as a rational strategy since they offer high structural predictability, great reaction control and direction as advantages, using the concept of chemical tailoring. On the other hand, rational synthesis focuses only on the molecular interactions during the process and rarely the factors that influence the reaction, especially in the preparation of the building blocks as it occurs as the first stage of the processes. In the present work, two different new methodologies were proposed to obtain building blocks based on chromium (III) and on the tripodal ligands 1,1,1-tris (hydroxymethyl)ethane (H3TME) and 1,1,1- tris(hydroxymethyl)propane (H3TMP). Single-crystal X-ray diffraction analyzes revealed dimeric structures with formula [Cr2(H2TME)2Cl4]∙2H3TME (CrMe) and [Cr2(H2TMP)2Cl4]∙2EtOH (CrEt). The crystalline structure of both compounds was studied through the analysis of intermolecular interactions using graph-set descriptors, Hirshfeld surfaces and fingerprint plots. In addition, the compounds were characterized by elemental analysis, absorption infrared spectroscopy, absorption uv-visible spectroscopy and electronic paramagnetic resonance. All spectroscopic characterization data were shown to be in perfect agreement with the structural data. CrMe obtained by Methodology 1 (CrMe-1) was used for a factorial study in which the optimal reaction conditions of temperature (80 °C), reaction time (24 h) and solvent volume solvent (acetonitrile; 10 mL) were determined. Empirical modeling, response surface and desirability function methods were carried determining that good yields, above 76.7%, can also be obtained under conditions of 95 °C, 15 h and 10 mL. Moreover, the antimicrobial activity for CrMe-1 complex was also evaluated, resulting 5.177 mmol∙mL-1 as the Minimum Inhibitory Concentration (MIC) and 20.71 mmol∙mL-1 as the Minimum Bactericidal Concentration (MBC), for Staphylococcus aureus, and 5.177 mmol∙mL-1 (MIC) for Escherichia coli, without MBC for this microorganism at the studied concentration. The present study contributes not only for the reporting of the novel CrMe structure, but also to the application of factorial analysis focused on inorganic synthesis and the results regarding the determination of the antimicrobial activity of chromium (III) complexes based on tripodal ligands, areas whose literature is still scarce.