Mechanosynthesis of Photochromic Oligophenyleneimines: Optical, Electrochemical and Theoretical Studies

Abstract

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.

Recent advances on carbazole-based photoinitiators of polymerization

“…The first product synthesized by mean of this reaction could be obtained in 95% yield. From an industrial point of view, this reaction is of crucial interest as this reaction is easy to perform, can be done in Green solvents such as ethanol and even in solvent-free conditions, by mechanosynthesis [98]. Irrespective of the synthetic approach, the side product of this reaction is safe and limited to a water molecule.…”

Mechanochemical Synthesis of Fluorinated Imines

“…Mechanochemical methodologies offer advantages over conventional synthetic routes with regard to the amount of solvents used and the energy consumed, and provide more efficient organic waste management; thus, they are becoming popular techniques for organic synthesis [ 23 , 24 , 25 ]. The preparation of imines by the mechanochemical approach has already been reported [ 26 , 27 , 28 , 29 , 30 ]. Synthetic protocols required the use of mills [ 27 , 28 , 29 , 30 ], catalytic amounts of iodine [ 27 ], workup of the obtained products [ 27 , 28 ] and long milling times (60 [ 30 ] or 90 [ 28 ] min).…”

“…The preparation of imines by the mechanochemical approach has already been reported [ 26 , 27 , 28 , 29 , 30 ]. Synthetic protocols required the use of mills [ 27 , 28 , 29 , 30 ], catalytic amounts of iodine [ 27 ], workup of the obtained products [ 27 , 28 ] and long milling times (60 [ 30 ] or 90 [ 28 ] min). Regarding the fluorine-containing imines, we found only one study on the mechanochemical strategy used for the synthesis of such compounds.…”

Electrochemical evaluation of conjugated oligophenylenimine in aqueous medium for bandgap determination

“…In this sense the CV technique has proven to be an efficient tool (Chooto, 2019;Sandford et al, 2019) to determine the electrochemical bandgap of organic compounds, as it describes the electronic transitions that occur during the excitation of the valence electrons of the conjugated molecule. In the research that precedes this paper is, the potentials determined in the redox processes for oligophenylenimine (DAFCHO, obtained for the mechanosynthesis technique) on glass/ITO in a BU 4 NPF 6 /ACN electrolyte gives an electrochemical bandgap value of 2.35 eV (Amado-Briseño et al, 2019). However, thus far, there have been not studies on the evaluation of the electrochemical bandgap of organic molecules in aqueous medium and substrate relatively more economical; such as the use of aqueous medium and the deposition of the organic semiconductor on glass substrates without ITO; that allows to eliminate the disadvantage for of obtained the electrochemical bandgap of organic compounds.…”