Photoswitching in nanostructured benzofuro[3,2-b]pyridin-9-ol and benzothio[3,2-b] pyridin-9-ol compounds as red- and yellow-light-emitting molecules: A TD-DFT approach

• The energetic and structural properties of benzofuro and benzothio derivatives were theoretically studied.
• M06-2X and PBE0 methods were used to study the ESIPT process.
• Potential energy curves in ground and excited states were calculated.
• The high Stokes shifts were expected in gas solvent media.
• The photophysical properties of the compounds were calculated in gas and solvent media.

In this work, intramolecular photo-induced proton transfer in Benzofuro[3,2-b]pyridin-9-ol (BFPO) and Benzothio[3,2-b] pyridin-9-ol (BTPO) were investigated using TD-DFT method at PBE0/6-311++G(2d,2p) and M06-2X/6-311++G(2d,2p) levels of theory. Both molecules are able to render both normal and tautomer emissions and exhibit the large Stokes-shifted fluorescence in gas and solvent media. The potential energy surfaces at ground and excited states, structural parameters, H-bonding energy, absorption and emission bands, vertical excitation and emission energies, oscillator strength, fluorescence rate constant, dipole moment, atomic charges and electron density at critical points were calculated. The effect of solvent media on electronics transition energies and absorption as well as florescence spectra are presented. The potential of these molecules as emissive materials in designing and generation of new displays and light sources were predicted based on their high Stokes shifts.

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