RESUMO
In this work a Metal-Organic Framework (MOF) was prepared using a solvothermal method, taking as precursors 1. 2-di-(4-pyridyl)-ethylene, 1.2.4.5-benzenetetracarboxylic acid and Co(No3)2-6H2O. This MOF was called UV-11 and was evaluated using microscopic, spectroscopic and electrochemical techniques. According to the obtained results, the melting point of the compound is located in a higher interval than its precursors. Stereoscopic microscopy analysis shows the presence of pink crystals in the form of needles. MEB technique displays a laminar morphology as well as crystals with approximate sizes (36 mm wide and 150 mm long). EDS analysis corroborated the presence of precursor elements such as cobalt, carbon and oxygen. Furthermore, the XRD technique shows the cobalt-related phases in the sample, which is cobalt bis (pyridine-6-carboxylic-2-carboxylate). A modified carbon paste electrode was prepared using MOF UV-11 and by cyclic voltammetry electrochemical technique, semi-reversible redox processes are identified, as well as thermodynamic and kinetic parameters were obtained with the Laviron equation, and electrochemical performance properties from the cyclic voltammetry experimental data.
RESUMO
In this work, two oligophenyleneimines type pentamers with terminal aldehydes, designated as DAFCHO (4,4'-((((((2,5-bis(octyloxy)-1,4-phenylene)bis(methanylylidene))bis(azanyl ylidene))bis(9H-fluorene-7,2-diyl))bis(azanylylidene))bis(methanylylidene))bis(2,5-bis(octyloxy) benzaldehyde)) and FDACHO (4,4'-((((((2,5-bis(octyloxy)-1,4-phenylene)bis(methanylylidene))bis (azanylylidene))bis(4,1-phenylene))bis(azanylylidene))bis(methanylylidene))bis(2,5-bis(octyloxy) benzaldehyde)) were synthesized by mechanochemistry method using 2,5-bis(octyloxy) terephtal aldehyde and 2,7-diaminofluorene or 1,4-phenylenediamine. All compounds were spectroscopically characterized using ¹H and 13C-NMR, FT-IR and mass spectrometry MALDITOF. The optical properties of the compounds were analyzed by UV-vis spectroscopy using different solvents. We observed that DAFCHO and FDACHO exhibit interesting photochromic properties when they are dissolved in chloroform and exposed to sunlight for 3, 5 and 10 min. The value of the energy band gap was calculated from the absorption spectra without irradiation Egap(optical). It was 2.50 eV for DAFCHO in chloroform solution, and it decreased to 2.34 eV when it is in films. For FDACHO, it was 2.41 eV in solution and 2.27 eV in film. HOMO (Highest Occupied Molecular Orbital), LUMO (Lowest Unoccupied Molecular Orbital) and Egap(electrochemical) values were obtained by electrochemical studies. The results indicate that the compounds can be considered as organic semiconductors since their values are 2.35 eV for DAFCHO and 2.06 eV for FDACHO. The structural and electronic properties of the compounds were corroborated with a DFT (Density Functional Theory) study.