Synthesis of Photochromic Oligophenylenimines: Optical and Computational Studies

Abstract

Phenyleneimine oligomers 4,4'-(((1E,1'E)-(((1E,1'E)-(1,4-phenylenebis-(azanylylidene))bis(methanylylidene))bis(2,5-bis(octyloxy)-1,4-phenylene))bis(methanylyl-idene))-bis(azanylylidene))dianiline (OIC1MS) and 7,7'-(((1E,1'E)-(((1E,1'E)-((9H-fluorene-2,7-diyl)bis(azanylylidene))bis(methanylylidene))bis(2,5-bis(octyloxy)-1,4-phenylene))bis- (methanylylidene))bis(azanylylidene))bis(9H-fluoren-2-amine) (OIC2MS) were prepared by means of conventional and mechanochemical synthesis and characterized by FT-IR, 1H- and 13C-NMR techniques. The optical properties of the compounds were studied in solution by using UV-visible spectroscopy, and the optical effects were analyzed as a function of solvent. The results show that OIC2MS exhibits interesting photochromic properties. Furthermore, the structural and electronic properties of the compounds were analyzed by TD-DFT. It was found that the mechanosynthesis is an efficient method for the synthesis of both tetraimines.

Mechanosynthesis of Photochromic Oligophenyleneimines: Optical, Electrochemical and Theoretical Studies

“…The results obtained show that both pentamers DAFCHO and FDACHO with aldehyde terminations have photochromic properties. In those with amine terminations named OIC1MS and OIC2MS [ 15 ] that we previously reported, only the pentamer produced by mechanosynthesis, with fluorene units in its structure, presents a photochromic effect. However, more studies are required to verify if this property is produced by the synthesis method, or by the structure of the oligomer under study.…”

“…The UV/visible spectra of DAFCHO and FDACHO were calculated substituting the aliphatic lateral chains by a methyl group, leaving the backbone with a methoxy group. This simplification only affects slightly the electronic transitions as they occur in the aromatic backbone [ 15 ].…”

“…The study of organic semiconductor compounds with photochromic properties is of great significance [ 1 ] in the manufacture of devices such as antireflective systems for screens [ 2 ], optical memory systems [ 3 ], optical switches [ 4 , 5 , 6 ], OFETs (Organic Field Effect Transistor) [ 7 , 8 ], smart windows [ 9 ] and a wide variety of sensors [ 10 , 11 , 12 ]. It has been shown that the photochromic response of organic materials depends on the functional groups type and on the molecule structure [ 1 , 13 , 14 , 15 , 16 ]. In previous studies, we reported on the reversible photochromic effect of imine-type materials, and we also reported on the type of terminal functional groups, as well as the synthesis method influencing these properties.…”

“…In previous studies, we reported on the reversible photochromic effect of imine-type materials, and we also reported on the type of terminal functional groups, as well as the synthesis method influencing these properties. [ 15 , 16 , 17 , 18 ]. A change in color is observed when imine type compounds were irradiated with sunlight; interestingly, the original color is recovered if the compound is placed in dark conditions.…”

“…A technique, such as mechanochemistry, that is free from solvents and catalysts and environmentally friendly would make these materials attractive for industrial production. This mechanochemistry technique has been successfully employed to obtain organic compounds that exhibit attractive optoelectronic properties [ 22 ] and has been proved to be efficient for obtaining imine oligomers [ 15 ].…”