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Modeling of cationic and excited states of boron difluoride acetylacetonate and eight of its γ-substituted derivatives was carried out using the methods of outer-valence Green's functions (OVGF), algebraic-diagrammatic construction for the polarization propagator of the second order (ADC(2)), coupled clusters with single and double excitations (EOM-CCSD), and time-dependent density functional theory (TDDFT/CAMB3LYP). Comparison of the calculated data with the absorption spectra made it possible to determine the influence of functional groups on the energies of electronic transitions and the nature of the absorption spectrum bands. Addition of the substituent SPh causes a decrease in the energy gap between the levels of the highest occupied and lowest vacant molecular orbitals, which determine the bathochromic shift of the long-wavelength band in the absorption spectrum relative to the other studied complexes. In the complexes containing Cl, Br, SCN, SEt, SPh and OS(O) 2 Ph groups in the γ-position, it was found that the highest occupied molecular orbitals are localized mainly on the substituents, and the lowest vacant molecular orbital corresponds to the chelate orbital π 4 , which determines the presence of transitions with charge transfer. It was shown that the calculated energies of excited states according to the ADC(2) method, in comparison with EOM-CCSD and TDDFT/CAMB3LYP, can be correlated with maxima of the experimental absorption spectra for the lowest average shift (0.27 eV). Image 1 • Nine boron difluoride β-diketonates were studied. • Complexes were studied by means of absorption spectroscopy. • The calculations were carried out using the Green's function and EOM-CCSD methods. • The experimental results were interpreted using quantum chemical computations. [ABSTRACT FROM AUTHOR]

[Display omitted] • Curcuminoids of boron difluoride have been synthesized. • Complexes studied by luminescence spectroscopy and DFT modeling. • Introduction of π-donor substituents increases luminescence quantum yield. • Dyes bio-imaging ability and cytotoxicity were investigated. Curcuminoids of boron difluoride, 1-aryl(hetaryl)-5-phenylpenta-2,4-dien-1-onates of boron difluoride, have been synthesized. A comparative study of the electronic structure, luminescent properties and their potential for applications in bio-imaging has been carried out. The influence of the electronic structure of α-substituents on the luminescence of compounds was studied by the methods of stationary and time-resolved luminescence spectroscopy and DFT modeling. The introduction of π-donor substituents leads to a noticeable bathochromic shift and an increase in the Stokes shift in the luminescence spectra. On going from σ-donor substituents in the phenyl ring to π-donor substituents, the luminescence quantum yield increases from 0.03 to 0.22. The maximum Stokes shift and high quantum yield of luminescence is exhibited by the complex with a stilbene substituent, which has the longest π-system and the maximum efficiency of charge transfer. Dyes are able to penetrate into the cells of the model cell line and accumulate, moreover, accumulation occurs mainly in the cytoplasm of cells. The compounds penetrate into the cells by 12 h of incubation without damaging it's structure and without causing rapid cell death. The submicromolar range of non-toxic concentrations during long-term incubation for a model cell line was determined, which is a characteristic of fluorescent imaging. Due to uniform distribution in the cytoplasm of cells dye with naphtyl substituent is promising for visualization of the cell cytoplasm. This leader compound has the lowest cytotoxicity for cells from the synthesized series of dyes, which makes it promising for further studies as a fluorescent imaging agent. The leader compound has the lowest cytotoxicity for cells from the synthesized series of dyes, which makes it promising for further studies as a fluorescent imaging agent. [ABSTRACT FROM AUTHOR]