Quantitative evaluation of thermodynamic parameters for thermal back-reaction after mechanically induced fluorescence change

Abstract

Kinetics of the thermal back-reaction of β-diketonate boron difluoride complexes after mechanical perturbation were evaluated by fluorescence intensity changes for the first time, suggesting that the activation parameters of the reaction intermediates governed intermolecular interactions such as 10 hydrogen bonding assisted by substituent groups. we studied and quantitatively evaluated for the first time the thermodynamic parameters for thermal back-reaction after mechanically induced fluorescence change. The molecular structure of boron difluoride β-diketonate complexes is shown in Chart 1. In this study we used 1-(4-tert-55 butylphenyl)-3-(4-methoxyphenyl)-1,3-propanedione (ab), 1,3-bis-(4-methoxyphenyl)-1,3-propanedione (2a), and 1,3-bis-(4-tert-butylphenyl)-1,3-propanedione (2b) as ligands. The boronation was performed by BF 3 ·OEt 2 in CH 2 Cl 2 according to a previous report. 12 The purification was carried out with column 60 chromatography. A 2.0×10 -3 mol·dm -3 dichloromethane solution was dropped on paraffin-coated weighing paper, and then the solvent-evaporated sample was used for spectroscopic studies. Fluorescence spectra were recorded on a Shimadzu RF-5300PC fluorescence spectrophotometer. In order to apply a mechanical 65 perturbation to the boron difluoride β-diketonate complexes, the samples were rubbed with a spatula. The temperature around the sample was controlled by a home-made system using a rubber heater (Hakko) and digital temperature controller (Omron E5CN-QT).

Recent progress of optical functional nanomaterials based on organoboron complexes with β-diketonate, ketoiminate and diiminate

“…In the case of boron diketonate, hydrogen bonding was disrupted by grinding, resulting in a less ordered polymorph. 43 As a result, MFC behaviors were observed. As mentioned above, the electronic structures of boron diketonates can be readily perturbed by the intermolecular interaction, leading to the alteration of the optical properties in the solid state.…”

Substituent-dependent backward reaction in mechanofluorochromism of dibenzoylmethanatoboron difluoride derivatives

“…We previously reported the mechanofluorochromic properties of BF 2 DBM derivatives in a communication. 26 The drop-casted abBF 2 powder exhibited blue emission with a 80 maximum at 460 nm. The fluorescence spectrum originated from the cyan crystal as previously observed.…”

Concentration-Dependent Fluorescence Color Tuning of the Difluoroboron Avobenzone Complex in Polymer Films

“…Dibenzoylmethanatoboron difluoride (BF 2 DBM) derivatives have excellent optical properties, for example, two-photon absorption cross-sections, 20,21 high fluorescence quantum yield in the solid state, 22 multiple fluorescence colors, [23][24][25]26,27 and reversible mechanofluorochromic properties. 28,29 In particular, BF 2 DBM based on the 4-tert-butyl-4′-methoxydibenzoylmethane (avobenzone) boron difluoride complex (BF 2 AVB) exhibits different emission depending on the crystal phase (polymorph). 30 BF 2 AVB also has excellent fatigue resistance by photoirradiation and a high fluorescence quantum yield even in the solid state (∼0.5), which is advantageous for photonics applications.…”