Issue 3, 2016

Substituent-dependent backward reaction in mechanofluorochromism of dibenzoylmethanatoboron difluoride derivatives

Abstract

The thermally backward reaction involved in the mechanofluorochromism of dibenzoylmethanatoboron difluoride (BF2DBM) derivatives, accompanied by an amorphous–crystalline phase transition, was quantitatively evaluated based on kinetics and thermodynamics. The kinetics was discussed by evaluation of the effect of temperature on the time-dependent changes of the fluorescence intensity for amorphous samples obtained by mechanical grinding. The thermodynamics was discussed based on data for the amorphous–crystalline phase transition obtained by differential scanning calorimetry. The enthalpy of activation (ΔH‡) of BF2DBM derivatives with MeO groups (2aBF2) was larger than that of derivatives with alkyl groups (2b-dBF2), whereas the entropy of activation (ΔS‡) was smaller than that of the derivatives with alkyl groups. It is proposed that the reaction dynamics of 2aBF2 will be governed by rotational motion around the C(methyl)–O bond. Interestingly, the Gibbs energies of activation (ΔG‡) were comparable for the reactions of all members of the BF2DBM series, though ΔH‡ and ΔS‡ were strongly dependent on the identity of the substituent. It is proposed that the substituent-dependent ΔS‡ term is one of the key parameters for understanding the mechanofluorochromism of BF2DBM derivatives associated with the amorphous–crystalline phase transition. These findings will also provide important insights into the process of formation of crystal nuclei in moving from the melted to the crystalline state.

Graphical abstract: Substituent-dependent backward reaction in mechanofluorochromism of dibenzoylmethanatoboron difluoride derivatives

Supplementary files

Article information

Article type
Paper
Submitted
10 Dec 2015
Accepted
09 Feb 2016
First published
11 Feb 2016

Photochem. Photobiol. Sci., 2016,15, 420-430

Substituent-dependent backward reaction in mechanofluorochromism of dibenzoylmethanatoboron difluoride derivatives

T. Sagawa, F. Ito, A. Sakai, Y. Ogata, K. Tanaka and H. Ikeda, Photochem. Photobiol. Sci., 2016, 15, 420 DOI: 10.1039/C5PP00453E

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Spotlight

Advertisements