Exciplex luminescence of difluoroboron meta- and para-Nitrodibenzoylmethanates in solutions and polymer matrix.

Molecular systems with intense exciplex luminescence are promising for the creation of OLEDs and light-transforming materials. The luminescent properties of difluoroboron meta- and para-nitrodibenzoylmethanates (1 and 2) were studied by the steady-state and time-resolved luminescence spectroscopy methods and quantum chemistry simulation. The influence of the position of the nitro group on the spectral properties of the complexes was revealed. The nitro group withdraws the electron density upon photoexcitation in the para-isomer in contrast to the meta-isomer. The bond order of the CC bond between the phenyl and chelate rings decreases in the excited relaxed state of 2, which leads to rotation of the substituent and a low quantum yield. Formation of exciplexes of 1 and 2 in benzene, toluene and polystyrene was found. The formation of the ground and excited-state electron donor-acceptor complexes based on difluoroboron nitrodibenzoylmethanates and benzene was revealed. The TDDFT method showed that the complexes are characterized by the presence of short contacts between the fluorine atom of the dye molecule and the hydrogen atoms of the aromatic hydrocarbon molecule. These contacts shorten during the transition from the ground state to the excited state. Polymeric compositions based on polystyrene (PS) and poly(methyl methacrylate) (PMMA) doped with 1 and 2 were obtained. The luminescence intensity of dyes 1 and 2 increases during the transition from PMMA to PS. A significant bathochromic shift of the luminescence maximum of 1 is observed, which is associated with the formation of exciplexes and triplexes. The obtained polymeric materials are promising for the development of optical smart materials.

Polymer films doped with boron difluoride ortho-hydroxydibenzoylmethanates: Solvatochromism and solvent-induced exciplex formation.

The spectral properties and solvatochromic behavior of boron difluoride ortho-hydroxydibenzoylmethanates in polymer matrices with different polarity (polystyrene, polyvinyl chloride, polycarbonate, poly(methyl methacrylate)) were investigated. The specific interaction of polystyrene, polycarbonate and poly(methyl methacrylate) with the investigated fluorophores was revealed. It was shown that the dyes are capable to form exciplexes with phenyl rings of polystyrene. The spectral properties of polystyrene films doped with boron difluoride ortho-hydroxydibenzoylmethanates, which were obtained by the pouring method, significantly depend on the solvent from which they were formed. This makes it possible to control the luminescence color of the films at the manufacturing stage.

Anthracene-containing complexes of boron difluoride. Dual luminescence, formation of excimers, and mechanochromism.

A comparative study of the luminescence properties and crystal structure of boron difluoride 1-(anthracen-9-yl)butane-1,3-dionate (1) and their nitrogen-containing analogs with hydrogen and methyl substituents (2 and 3) has been performed. For boron difluoride beta-diketonate (1) and beta-ketoiminate with a hydrogen substituent (2), which does not create significant steric difficulties, the luminescence of crystals is determined by that of excimers and aggregates based on them. For the compounds 1-3, mechanofluorochromism has been observed, the spectral manifestation of which is different: at grinding the crystals of 1 and 2, a hypsochromic shift of the excitation and luminescence bands occurs, whereas in the case of crystals of 3, a bathochromic shift takes place. Dual luminescence has been detected for the solutions of 1. During the relaxation in the excited state of a molecule of 1 (S1 â†’ S'1), TICT is formed. It was possible to register the short-wavelength luminescence from the LE state in the dilute solutions of 1. TICT or LE luminescence can be excited, in the case of 1, by varying the wavelength of the exciting light.

Design, Synthesis, and Crystallization-Induced Emission of Boron Difluorides ß-Ketoiminates.

A series of new nitrogen-containing analogues of boron difluoride benzoylacetonates with hydrogen and methyl substituents at the nitrogen atom have been synthesized. A comparative study of boron difluoride ß-ketoiminates and their oxygen-containing analogues by means of luminescence and IR spectroscopic methods as well as quantum chemistry simulations was also performed.

Nitrogen-Containing Analog of Dibenzoylmethanate of Boron Difluoride: Luminescence, Structure, Quantum Chemical Modeling, and Delay Fluorescence.

Boron difluoride of 3-amino-1,3-diphenyl-2-propene-1-onate (1) has been synthesized and its crystal structure has been determined. The comparative studies of 1 and its oxygen analog 1,3-diphenyl-1,3-dionate (dibenzoylmethanate) of boron difluoride (2) have been performed using the methods of stationary and time-resolved spectroscopy and quantum chemical modeling. It was established that at the transition from solutions to crystals, a bathochromic shift of the spectra and a significant increase of luminescence intensity of 1 take place. The luminescent properties of solutions of 1 and 2 are similar. The peculiarities of crystal packings of 1 and 2 are responsible for differences in crystals luminescent properties. For crystals of 2, one observes the luminescence of J-aggregates and excimers, while for 1, in which a dimer is an elementary structural fragment, only the excimer luminescence is registered. A delayed excimer fluorescence of the P-type was observed for crystals of 1 and 2 at room temperature. The intensity of the delayed fluorescence of 1 is 300-fold higher than that of 2. Graphical Abstract Luminescence of J-aggregates and the formation of excimers in crystals of 1 and 2.