Mechanofluorochromic Materials Based on Aggregation-Induced Emission-Active Boron Ketoiminates: Regulation of the Direction of the Emission Color Changes

• Published in: Chemistry : a European journal 2015-05, Vol.21 (19), p.7231-7237
• Main Authors: Yoshii, Ryousuke, Suenaga, Kazumasa, Tanaka, Kazuo, Chujo, Yoshiki
• Format: Article
• Language: English
• Subjects: aggregation-induced emission; Bands; Boron; Chemistry; Crystal structure; Differential scanning calorimetry; Diffraction; Emission; heterocycles; mechanochromism; Phase shift; Phase transitions; thermochromism; X-rays
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201500033

We report a series of mechanofluorochromic (MFC) compounds based on organoboron complexes with aggregation‐induced emission (AIE) characteristics. We synthesized a variety of boron ketoiminates and investigated the effect of the substituents on the optical properties by altering the end groups in the compounds. The synthesized boron ketoiminates showed AIE properties and MFC behavior. Interestingly, the hypsochromic and bathochromic shifts of the emission bands individually observed for boron ketoiminates depended on the chemical structures of the end groups. From the X‐ray diffraction and differential scanning calorimetry analyses, it was confirmed that the MFC property of boron ketoiminates should be derived from a phase transition between crystalline and amorphous states. In addition, the direction of the peak shifts of the emission bands was controlled by the degree of steric hindrance of the end group. Scratch that! A series of aggregation‐induced emission (AIE)‐active boron ketoiminates with mechanofluorochromic (MFC) properties have been synthesized. From the X‐ray diffraction and differential scanning calorimetry analyses, it was suggested that the MFC property derives from a phase transition between the crystalline and amorphous states, and the direction and extent of the peak shift can be controlled by changing the end group (see figure).