Styryl dye possessing donor-π-acceptor structure – Synthesis, spectroscopic and computational studies

• Synthesis of donor-π-acceptor dyes is described and characterized.
• The one- and two-photon spectroscopic measurements are presented.
• The experimental results are in good agreement with quantum chemical calculations.
• The dyes have good two-photon properties.

A novel hemicyanine dye possessing donor-π-acceptor structure that features a fixed benzimidazole ring as an electron donor and pyridinium moiety as an electron acceptor was synthesized. The structure of the hemicyanine was elucidated by means of NMR and IR spectroscopy. The dye was studied using steady-state absorption and emission spectroscopy. The analysis of experimentally recorded spectra was supported by quantum chemical calculations using density functional theory with CAM-B3LYP, LC-BLYP, LC-ωPBE and PBE0 functionals. The measurements and calculations were performed in solvents of different polarity. In particular, we found that the CAM-B3LYP and LC-ωPBE excitation energies are in very good agreement with the experimental data. Two-photon absorption of the dye was studied by Z-scan measurements.