A trigonal molecular assembly system with the dual light-driven functions of phase transition and fluorescence switchingElectronic supplementary information (ESI) available: DSC traces, optimized C3-symmetric and asymmetric 3BuAz structures, SEM images and sphere size distribution as a function of concentration, UV-vis absorption spectral changes, photopatterning, two-dimensional GI-XRD, OM and FOM images, crystallographic data in CIF, and NMR data. CCDC 1872750. For ESI and crystallographic dat

• Main Authors: Abe, Ikue, Hara, Mitsuo, Seki, Takahiro, Cho, Sung June, Shimizu, Masaki, Matsuura, Kazunori, Cheong, Hae-Kap, Kim, Jin Young, Oh, Jihun, Jung, Jaehoon, Han, Mina
• Format: Article
• Language: English
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/c8tc05701j

The design of light-responsive fluorescent assembly systems with a variety of photochemical and photophysical properties is important for the fundamental understanding of the assembly-disassembly process as well as for applications such as optical information storage and fluorescence sensing. A major obstacle in constructing such photofunctional materials is the lack of a molecular design strategy for photoswitchable organic chromophores with aggregation-induced emission/aggregation-induced emission enhancement (AIE/AIEE) characteristics. Herein, we describe a new trigonal azobenzene framework showing AIE/AIEE characteristics and excellent photoisomerization (∼90%) from the C 3 -symmetric to asymmetric (including a bent-shaped cis -azobenzene) form. NMR experiments demonstrate light-induced molecular structure changes, which cause drastic symmetry breaking. The trigonal chromophores assemble into red fluorescent microspheres and their fluorescence intensity increases by ∼10-fold, confirming the AIE/AIEE characteristics. Importantly, scanning electron microscopy (SEM), optical microscopy (OM), and fluorescence optical microscopy (FOM) images substantiate that a noticeable light-driven melting occurs simultaneously with a marked fluorescence switching from on to off. Moreover, the fluorescent spheres are successfully applied in optical information storage and fluorescence sensing in a non-contact fashion. A trigonal azobenzene framework showing AIE/AIEE and photoisomerization was synthesized to form fluorescent microspheres exhibiting light-driven phase transition and fluorescence switching.