Synthesis and Photophysical Properties of Alkoxysilyl Derivatives of Dibenzoylmethanatoboron Difluoride

Abstract

Alkoxysilyl derivatives of dibenzoylmethanatoboron difluoride (DBMBF2) are synthesized by the hydrosilylation reaction of the corresponding O‐allyl derivatives of DBMBF2 with triethoxysilane. The photophysical properties of the synthesized O‐allyl and alkoxysilyl derivatives are investigated. It is found that the absorption and fluorescence spectra of the DBMBF2 derivatives essentially depend on the position of the O‐allyl or O‐propyl alkoxysilyl substituent. The highest fluorescence quantum yield is obtained for the para‐position, whereas the substitution at the meta‐position gives the largest bathochromic shift in the fluorescence spectrum. Density functional theory calculations of the structures and time‐dependent density functional theory calculations of the gas‐phase excitation and emission energies of alkoxysilyl derivatives are performed at the PBE0/SVP level of theory. Some spectral features of para‐, ortho‐, and meta‐substituted derivatives can be adequately explained by the overlapping of two absorption bands.

Vibronic bandshape of the absorption spectra of dibenzoylmethanatoboron difluoride derivatives: analysis based on ab initio calculations

“…44 Similar calculations were performed with the B3LYP functional. The vertical transition energies agreed well with experiment, but, similarly to the literature, 44 the oscillator strengths for the ortho-and meta-isomers were incorrect (Table 2). Therefore, we decided to perform all further calculations with the CAM-B3LYP functional.…”

“…Unlike the rigid dyes investigated in the literature, 46 the chromophore moiety in substituted DBMBF 2 dyes can adopt different conformations, which can absorb at different wavelengths. 44 that the PBE0 functional poorly reproduces the oscillator strengths and relative positions of some peaks for DBMBF 2 derivatives. The determination of the nature of individual peaks and their spectral broadening associated with a certain substituent in the spectra of such dyes solely from experimental data is problematic.…”

“…44 On the basis of these calculations, it was suggested that the above-mentioned spectral features of p-, o-, and m-substituted derivatives might be explained by an overlap of two electronic absorption bands. 44 On the basis of these calculations, it was suggested that the above-mentioned spectral features of p-, o-, and m-substituted derivatives might be explained by an overlap of two electronic absorption bands.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] These approaches have been successfully applied to calculations of spectral band shapes for a large number of systems containing both inorganic [3][4][5][6][7] and organic [21][22][23][24][25][26][27][28] chromophores. The electronic absorption and fluorescence spectra of DBMBF 2 and its methyl, allyloxy, and alkoxysilyl derivatives were investigated in polar and nonpolar solvents, 35,42,44 and their fluorescence quantum yields, lifetimes, and vibronic structure were reported. 29,30 Therefore, the theoretical prediction of absorption or emission band shapes of various chromophores and their changes upon interaction with analytes is very important for the design and selection of materials for optical chemical sensors.…”

“…44 The spectra of allyloxy and propyloxysilyl derivatives are red-shifted by ~700 cm −1 . 44 The spectra of allyloxy and propyloxysilyl derivatives are red-shifted by ~700 cm −1 .…”