title: Color- and morphology-controlled self-assembly of new electron-donor-substituted aggregation-induced emission compounds.
abstract: Four electron-donor-substituted aggregation-induced emission (AIE) compounds, N,N'-bis(4-methoxylsalicylidene)-p-phenylenediamine (BSPD-OMe), N,N'-bis(4-methylsalicylidene)-p-phenylenediamine (BSPD-Me), N,N'-bis(salicylidene)-p-phenylenediamine (BSPD), and N,N'-bis(4-hydroxylsalicylidene)-p-phenylenediamine (BSPD-OH), are designed and synthesized. They are all found to exhibit controlled self-assembly behaviors and good thermal properties. By changing the terminal electron-donor groups, they are controlled to self-assemble into three emission colors (green, yellow, and orange) and four morphologies (microblocks, microparticles, microrods, and nanowires) in THF/water mixtures. Their self-assembled structures were investigated with scanning electron microscopy (SEM), fluorescent microscopy images, transmission electron microscopy (TEM), and powder X-ray diffraction (PXRD) techniques. In addition, the emission colors of BSPD-OH can be successfully controlled to three colors (green → yellow → orange) through simply changing the water fraction (fw). Their thermal gravimetric analysis (TGA) results indicate that their thermal decomposition temperatures (Td, corresponding to 5% weight loss) range from 282 to 319 °C. Their differential scanning calorimetry (DSC) data show that BSPD-OH bears a glass-transition temperature (Tg) of 118 °C. The good Td and Tg values will ensure them to be luminogens for organic light-emitting diodes (OLEDs). The theoretical calculations and single-crystal X-ray diffraction (XRD) analysis of BSPD-OMe and BSPD suggest that the stronger electron donor substituent can twist the molecular conformation, decrease the degree of π conjugation, increase the energy gap, and then induce the emission colors' blue shift and morphology variation. The results are meaningful in controlling the emission colors and self-assembly shapes of these derivatives, and they also provide a novel but facile way to get color-tunable AIE luminogens for OLEDs.
authors.affiliation: Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry and ‡Analytical and Testing Center, Beijing Normal University , Beijing 100875, China.
authors.forename: Caixia
authors.initials: C
authors.lastname: Niu
authors.forename: Liu
authors.initials: L
authors.lastname: Zhao
authors.forename: Tao
authors.initials: T
authors.lastname: Fang
authors.forename: Xuebin
authors.initials: X
authors.lastname: Deng
authors.forename: Hui
authors.initials: H
authors.lastname: Ma
authors.forename: Jiaxin
authors.initials: J
authors.lastname: Zhang
authors.forename: Na
authors.initials: N
authors.lastname: Na
authors.forename: Jingsa
authors.initials: J
authors.lastname: Han
authors.forename: Jin
authors.initials: J
authors.lastname: Ouyang