Síntese, caracterização e estudos para aplicação de complexos com ligante derivado de 2-Furil-3-Hidroxicromona e cloreto de nicotinoíla

Abstract

Chromones are naturally occurring compounds with a range of biological activities and unique spectroscopic properties, such as light emission and intense bands in the fluorescence spectrum. In this sense, this work presents the synthesis and characterization of nicotinoil-2-(furan-2-yl)-4-oxo-4H-chromen-3-one (N-3EC-F) and its complexes with metal ions from the first transition row. The ligand was obtained from the reaction of a furyl-substituted 3-hydroxychromone with nicotinoyl chloride, and characterized by FT-IR, MS and 1H and 13C NMR. In the next step, reactions were carried out for the synthesis of complexes with the ligand N-3EC-F, with which 5 complexes with different metal chlorides were obtained: [M(N-3EC-F)2Cl2]n (M = Mn2+ (1), Fe2+ (2), Co2+ (3), Ni2+ (4) and Cu2+ (5)). Compound 1 had its structure calculated from powder X-ray diffraction data and it has been proposed that compounds 2─5 are isostructural to 1. New Cu2+ complexes were also obtained when copper(II) sulfate or nitrate were used, in the presence of potassium halides or pseudohalides. These complexes are possibly anionic with formulas K2[Cu2(N-3EC-F)2(SO4)2X2] (X = Br (5s1), I (5s2) or SCN (5s3)), K2[Cu2(N-3EC-F)2(NO3)3X3] (X = Br (5n1) or I (5n2)) and K3[Cu(N-3EC-F)(NCS)(NO3)4] (5n3). The modification in the synthesis with copper(II) sulfate and KSCN led to a new compound with formula [Cu(N-3ECF)2(NCS)2]n, whose structure was elucidated by single-crystal X-ray diffraction. All coordination compounds were characterized by FT-IR, which showed displacement in the stretch bands of carbonyl and C═N, and presence of bands referring to the stretch S═O and C≡N, of sulfate and thiocyanate, respectively, when it was the case. Powder X-ray diffraction analyzes were also performed, which showed similar diffraction patterns for compounds 1‒5, 5s1 and 5s2, and 5n1 and 5n2. To understand the chemical composition of the complexes, elemental and EDS analysis were performed, which showed the presence of metal for all compounds, chlorine for 1‒5, sulfur for 5s1─5s3, the respective halogen and potassium, for all that were obtained from the synthesis that took potassium halides. UV-Vis spectra in DMF solution were performed for the ligand and complexes 1 and 5, which indicated that, in solution, the ligand is uncoordinated. The study of diffuse reflectance was carried out to know the estimated band gap of the materials, which was in a range of 3.29‒3.38 eV, in order to analyze a potential application in the field of photocatalysis. To perform the photocatalytic tests, TiO2-1─ TiO2-5 composites were prepared, and the best result was obtained when using the TiO2-5 composite, in which the production of H2 was 2985 μmol H2/g photocatalyst. Finally, a study of the antimicrobial activity of compounds 1‒5 was carried out, and the best results, when compared to the performance of sulfamethoxazole, were of compounds 1, 4 and 5 against M. fortuitum.