Molecular design of −substituted boron difluoride curcuminoids: Tuning luminescence and nonlinear optical properties

Boron β-diketonates are prospective fluorescent dyes for functional organic materials to new technologies in the fields of chemistry, NLO-optics, photonics and bio-imaging. The novel NIR-to-NIR luminophors – curcuminoids of boron difluoride with different substituents at the central carbon atom (at the γ-position) of the chelate ring 1,7-bis(4′-N,N′-dimethylaminophenyl)-4-organyl-gept-1,6-dien-3,5-dionate of boron difluoride (1–5) were synthesized. Luminescence in solutions, crystals and polymer matrices, photobiological properties and NLO properties in polystyrene (PS) and polymethylmethacrylate (PMMA) were studied. The crystal structure has been determined for 1. For 1–5, in PS film, upon excitation by laser (365 nm), two luminescence bands are observed in the blue (430 nm) and red (650–700 nm) regions of the spectrum. For 1–5, two-photon luminescence is recorded in PS and PMMA films. PS 1 films demonstrate high photostability. The synthesized dyes turned out to be almost non-toxic for HCT116 tumor cells both in a long-term dark experiment (72 h) and after photoexcitation in accordance with absorption maxima in the submicromolar concentration range. The compounds were rapidly accumulated by cells within 3 h, demonstrating cytoplasmic distribution and the potential for use as cellular photoimaging agents. The accumulation of dyes with hydrocarbon γ-substitutes (methyl, iso-propyl, phenyl) after 3 and 24 h is more effective compared to dye 2 (commercial product Cranad-2).