The crystal structure, luminescence properties of 2,2-difluoro-4,6-(4-methylphenyl)-1,3,2-dioxaborine (СH 3 C 6 H 4 COCHCOC 6 H 4 CH 3 BF 2 ) crystals and solutions at different concentrations are examined at T 296 K and 156 K.Keywords: boron difluoride β-diketonate, 2,2-difluoro-4,6-(4-methylphenyl)-1,3,2-dioxaborine, crystal structure, luminescence, H and J aggregates, quantum chemical simulation.Boron difluoride β-diketonates exhibit strong luminescence in both solutions and the crystalline state [1]. These compounds are employed in molecular electronics for they possess nonlinear optical properties [2], two-photon absorption [3,4], and photoconductivity [5].2,2-Difluoro-4,6-(4-methylphenyl)-1,3,2-dioxaborine (СH 3 C 6 H 4 COCHCOC 6 H 4 CH 3 BF 2 ) (1) belongs to boron difluoride dibenzoylmethanates bearing substituents in the phenyl rings. We have previously studied the spectral luminescent properties of solid boron difluoride dibenzoylmethanate (C 6 H 5 COCHCOC 6 H 5 BF 2 ) and its solutions [6]. The introduction of a methyl substituent, as exemplified by boron difluoride benzoylacetonate [7], strongly influences the supramolecular structure of the crystal, its luminescence properties being significantly affected. This contribution reports the effect of the crystal structure of 1 on its spectral luminescence properties as well as the evolution of spectral properties with an increase in the solution concentration.
EXPERIMENTALCompound 1 was prepared by acylation of toluene with mixed anhydride of trifluoroacetic and malonic acids [8] (Scheme 1). X-ray quality crystals of 1 were obtained by recrystallization from toluene on slow cooling of the solution.Luminescence spectra of the crystals were recorded on a SDL-1 spectrometer (LOMO) at 300 K and 77 K, excitation source DRSh-250 lamp, UFS-6 filter (λ ex = 365 nm); excitation spectra and luminescence spectra of the solutions and crystals at 300 K were measured on a Shimadzu-RF5301 spectrofluorophotometer. Time-resolved luminescence spectra were recorded on a FluoTime 200 spectrometer (PicoQuant). A crystal with the dimensions of 10×1.35×0.6 mm was used for the time-resolved spectroscopic examination of compound 1. Complete X-ray structural investigation was carried out with a SMART-1000 CCD diffractometer (Bruker) at temperatures of 296(2) K and 156(2) K. Data collection for the crystal was carried out by ω-scanning in three sets of 906