Photo-physical effects of the chemical insertion of the dimethyl-amine moiety on the newly synthesized oligophenylene (OMPA)

The synthesized oligo [4-(methoxyphenyl) acetonitrile] (OMPA) was chemically modified by Knoevenagel condensation of OMPA with dimethylformamide dimethyl acetal (DMF-DMA). The obtained oligomer is composed of short chains of poly [3-(dimethylamino)-2-(4-methoxyphenyl)acrylonitrile] and denoted OMFA. Experimental measurements: ultraviolet-visible (UV-vis), steady-state and time-resolved photoluminescence spectroscopies, infrared spectroscopy, and thermogravimetric analysis (TGA), were combined with theoretical calculations, based on density functional theory (DFT) methodologies, to highlight the effect of the grafting of the dimethyl-amine group on the photo-physical and electronic properties of the as-synthesized oligomer. Thus, a redshift of the absorption and photoluminescence spectra is observed upon the chemical grafting of the functional group. Added to that, a decrease of the optical bandgap (E-g(opt)) and the energy gap EH-L=E-HOMO-E-LUMO occurs upon the chemical modification. DFT computations show that the chemical insertion of the dimethyl-amine group into the monomer and the oligomer induces a drastic change on their frontier orbitals HOMO and LUMO. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The chemical modification of the synthesized oligo [4-(methoxyphenyl) acetonitrile] by Knoevenagel condensation with dimethylformamide dimethyl acetal resulted in significant changes to the photo-physical and electronic properties, including a redshift in absorption and photoluminescence spectra, a decrease in optical bandgap and energy gap, and drastic alterations in the HOMO and LUMO frontier orbitals.