Arene effects on difluoroboron β-diketonate mechanochromic luminescence

Abstract

Difluoroboron b-diketonate (BF 2 bdk) dyes display reversible mechanochromic luminescence (ML) in the solid state. A series of BF 2 bdk dyes with methyl, phenyl, naphthyl and anthracyl groups (i.e. arene substituents and bdk ligands: Me-Ph ¼ mbm, Ph-Ph ¼ dbm, Np-Ph ¼ nbm, An-Ph ¼ abm) were prepared to test the effects of p conjugation length and arene size on ML properties. Solid-state emission spectra were recorded for powders, spin-cast films, and dye coated weighing paper. The materials emit at various wavelengths from blue to red, depending on the conjugation length. Additionally, emission spectra were recorded for smeared solids and their recovery was tracked at room temperature over time. All dyes except for BF 2 mbm show emission changes upon mechanical perturbation, with increasing p conjugation correlating with more dramatic, redshifted fluorescence, however, their recovery is significantly affected by the aromatic substituents. The thermal and structural properties of the dyes in the solid state were also investigated by differential scanning calorimetry (DSC) and atomic force microscopy (AFM).

Aromatic Difluoroboron β-Diketonate Complexes: Effects of π-Conjugation and Media on Optical Properties

“…Diketone ligands were prepared by Claisen condensation using NaH and boron complexes were prepared using BF 3 etherate as previously described. The data of complexes 1 - 4 , 39 5 , 31 6 , 13 9 , 13 10 31 are in accord with the literature. The synthesis of complexes 7 and 8 is described below.…”

“…The synthesis and solid-state fluorescence and mechanochromic properties for compounds 1 - 4 have been described elsewhere. 39 …”

Stimuli responsive furan and thiophene substituted difluoroboron β-diketonate materials

“…1,2 Difluoroboron β-diketonate (BF 2 bdk) complexes are of particular interest due to their impressive emission properties and the facile synthesis of β-diketonates via Claisen condensation from a variety of commercially available ketones and esters. 1,3-7 Desirable properties of BF 2 bdks include high extinction coefficients, 8-10 high quantum yields, 8-10 two-photon absorption cross-sections, 8,11 a range of emission colors in solution and the solid state, 10,12 solvatochromism, 4 and the ability to impart significant intramolecular charge transfer (ICT) character in unsymmetrical analogues. 13 Previously we reported the unique mechanochromic luminescent (ML) properties 6,7,12,14,15 of BF 2 bdk dyes as well as their ability to act as dual-emissive ratiometric oxygen sensors in polymer media.…”

“…Aryl substituted BF 2 bdks with donor-acceptor motifs typically exhibit high-contrast, reversible ML. 12,14,22 …”

The crystal structure of bis(2-(2,2,2-trifluoroacetyl)-3,4-dihydronaphthalen-1-olato-κ2O,O′)copper(II), C24H16CuF6O4

“…The title complex was synthesized according to the literature [3]. A mixture of 2-(2,2,2-trifluoroacetyl)-3,4-dihydronaphthalen-1(2H)-one (0.5 g, 2.06 mmol) and NaOH…”