Luminescence and Reversible Luminescence Thermochromism of Bulk and Microcrystals of Dibenzoylmethanatoboron Difluoride

Abstract

Essential differences in the luminescence properties of dibenzoylmethanatoboron difluoride (1) bulk and microcrystals were detected. Analysis of the spectral data showed that in every case the fluorescence spectrum of 1 consisted of three components: monomer fluorescence, excimer fluorescence, and fluorescence related with interdimer interaction. Evolution of luminescence spectra observed with decrease of the crystal size are bound with decrease of monomer fluorescence intensity and considerable growth of intensity of fluorescence related to interdimer interaction. The presence of reversible luminescence thermochromism was discovered for 1: lowering the temperature from 300 to 77 K resulted in essential hypsochromic shift of the luminescence band maximum ( approximately 60 nm) connected with considerable decrease of the distances between the planes of the neighboring molecules ( approximately 0.1 Angstrom) that lead to the weakening of interdimer interaction and intensification of monomer luminescence.

Reversible luminescence thermochromism and phase transition in crystals of thiophenylacetylacetonatoboron difluoride

“…Unlike respective 1,3-dicarbonyl compounds, b-diketoboron difluorides shows an intensive luminescence both in solutions and in crystals [3]. This class of compounds is characterized by excimer luminescence observable as in solutions and as in crystals [4,5], moreover, luminescent thermochromism and size-dependent luminescence were observed in some crystals [6][7][8]. The optic properties of b-diketonatoboron difluorides crystals are closely connected with their molecular architecture [5,9].…”

Size‐dependent fluorescence of dibenzoylmethanate and ditoluylmethanate of boron difluoride

“…4b). Similarly to DBMBF 2 (13), the comparable spectral analysis of the DTMBF 2 solutions and its crystals showed that the fluorescence spectra of crystals included components connected with monomeric and excimeric emission and those corresponding to interdimeric interaction. Contrary to DBMBF 2 (Fig.…”

“…It was early (13) detected that the fluorescence spectrum of DBMBF 2 consisted of three components with maxima at 470, 500 and 560 nm, and the short-wave component (470 nm) was assigned to monomeric fluorescence, the middle-wave component (500 nm) to excimer fluorescence and the long-wave component (560 nm) to the fluorescence connected with interdimeric interaction. Thus, the fluorescence colour change corresponds to the relative intensity changes of spectral components: sharp intensity decreases of monomeric fluorescence and essential increases of fluorescence due to interdimeric interaction were observed with decreasing size of the DBMBF 2 crystals.…”

Size-dependent luminescence of boron difluoride β-diketonates

“…A band with a maximum at 456 nm, which appears in the spectrum of bulk crystal of 1 grown in the polymer matrix (crystal size d = 150 μm), matches the fluorescence band of monomers. 11 The spec tra of microcrystals of 1 (d = 1-3 and 10 μm) exhibit a band with a maximum at 535 nm, which corresponds to fluorescence of excimers. 16 An interesting feature is the difference between the fluorescence spectra of the bulk crystals grown in solution (d = 500 μm) and in the poly mer matrix (see Fig.…”

“…Earlier, 11 we have reported the dependence of the luminescence properties of (dibenzoylmethanato)boron difluoride (1) on the crystal size. Here we present the results of studies on size dependent fluorescence of bo ron difluoride β diketonates of the general formula (R 1 COCHCOR 2 )BF 2 (1-8, Table 1).…”