Aggregation-induced emissions in the mesogenic BF2 complexes of aroylhydrazines

• Published in: New journal of chemistry Vol. 45; no. 28; pp. 12557 - 12568
• Main Authors: Cai, Yi-Hong, Chih, Hsin-Yun, Lee, Gene-Hsiang, Lai, Chung K.
• Format: Journal Article
• Language: English
• Published: CAMBRIDGE Royal Soc Chemistry 28.07.2021; Royal Society of Chemistry
• Subjects: Boron; Chemistry; Chemistry, Multidisciplinary; Crystal structure; Crystallography; Dichloromethane; Dihedral angle; Infrared spectroscopy; Light emission; Molecular structure; Optical properties; Physical Sciences; Science & Technology; Signal processing; X ray analysis; BORON COMPLEXES; RED; FLUORESCENT; DYES; ENHANCEMENT; COORDINATION; DERIVATIVES; ARRANGEMENTS; PROBE; AIE
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/d1nj02001c

Herein, we report the synthesis of two new families of borondifluoride complexes derived from aroylhydrazines and the investigation of their mesomorphic and AIE properties. The crystallographic structure of the mesogenic complex 1a-BF2 (n = 8) was determined by X-ray analysis; it crystallizes in the P1 triclinic space group and the geometry of boron atoms is tetrahedral. The crystal is considered to be linear-shaped with a length of L similar to 33.92 angstrom. A relatively small dihedral angle of ca. 3.30 degrees-5.75 degrees was observed between both neighboring phenyl groups and tetrahedral BF2 moiety. Mesomorphic properties were crucially impacted by the structure of the terminal group. Ligands 1a-b were not mesogenic; however, both the series of 1a-BF2 and 1b-BF2 complexes formed SmC or/and N phases. The H-bonding interactions are attributed to the occurrence of mesomorphism in compounds 1-BF2, which was supported by FT-IR spectroscopy. The optical property of the boron complexes is related to their molecular structures, and they emitted blue-to-green emissions at lambda(max) = 445-466 nm in CH2Cl2. Compounds 1a-BF2 aggregated in higher water fractions (f(w)), which turned on their light emission process, whereas weak PL signals were recorded at f(w) < 50% because the luminogen was fully dissolved and quenched in these solvent compositions. The PL intensity was enhanced at f(w) > 60% until it reached the maximum intensity at f(w) similar to 90%. Thus, compound 1a-BF2 is AIE active.