Tris(2-hydroxyphenyl)triazasumanene: bowl-shaped excited-state intramolecular proton transfer (ESIPT) fluorophore coupled with aggregation-induced enhanced emission (AIEE)

• Published in: Materials chemistry frontiers 2018, Vol.2 (3), p.514-519
• Main Authors: Kaewmati, Patcharin, Yakiyama, Yumi, Ohtsu, Hiroyoshi, Kawano, Masaki, Haesuwannakij, Setsiri, Higashibayashi, Shuhei, Sakurai, Hidehiro
• Format: Article
• Language: English
• Subjects: Agglomeration; Aggregates; Chemical synthesis; Emission analysis; Protons; Single crystals; X ray powder diffraction
• ISSN: 2052-1537; 2052-1537
• DOI: 10.1039/C7QM00530J

Tris(2-hydroxyphenyl)triazasumanene (( A )-(+)- 1 ), a bowl-shaped molecule, which possesses 2-(2′-hydroxyphenyl)pyridine moieties, was successfully synthesised. ( A )-(+)- 1 showed a single peak emission in CH 2 Cl 2 , which overlapped with the emission of the triazasumanene skeleton and diminished at a high concentration, corresponding to the formation of the excited enol form. In contrast, single crystals of ( A )-(+)- 1 exhibited a dual emission with a large Stokes shift, indicating the presence of the excited keto form by the excited state intramolecular proton transfer (ESIPT) process. In the solution of ( A )-(+)- 1 containing a mixture of a large amount of a poor solvent (hexane or MeOH) and a small amount of CH 2 Cl 2 , colloidal aggregates emerged with the continuous increment of emission intensity by further addition of the poor solvent, demonstrating aggregation-induced enhanced emission (AIEE). The analysis of the morphology and the structure of the aggregates using a scanning electron microscope (SEM) and powder X-ray diffraction (PXRD) revealed the well-ordered structure of the aggregates, which possessed a molecular packing pattern similar to that of an ( A )-(+)- 1 single crystal.