Handbook of Aggregation-Induced Emission, Volume 3. Группа авторов

Figure 2.21 (a) Schematic illustration of the co‐assembly processes. (b) Molecular structure of chiral gelator 65. (c) Molecular structures of achiral AIEgens.

      Source: Reproduced with permission [51]. Copyright 2019, Wiley‐VCH.

Figure 2.22 Schematic illustration of the co‐assembly of molecules 66 and 67 under different molar ratio.

      Source: Reproduced with permission [52]. Copyright 2019, The Royal Society of Chemistry.

In 2019, Tang’s group reported a unique CPL‐active supramolecular system based on the co‐assembly of a chiral BINOL‐derived gold complex 68 (Figure 2.23a) and three achiral luminophores (Figure 2.23b) [55]. Chiral complex 68 formed helical fibers through a long‐time self‐assembly process, and the chirality was controlled by the chirality of the gold complex. R‐68 formed M‐type helical fibers, while S‐68 formed P‐type helical fibers. However, no obvious CPL signal was observed for these helical fibers. Interestingly, the co‐assembly systems comprised of the chiral gold complex and achiral luminophores exhibited strong CPL signals with different colors (410–560 nm) and relatively high g_lum up to 5 × 10⁻³ (Figure 2.23c). In 2019, Han and coworkers prepared CPL‐active AIEgen‐silica hybrid hollow nanotubes through a spontaneous chiral self‐assembly process in the absence of symmetry‐breaking agent [56]. These nanotubes revealed a helical structure and exhibited CPL around 450 nm with |g_lum| up to 2 × 10⁻².

Figure 2.23 (a) Molecular structures of chiral gold complex enantiomers R‐68 and S‐68. (b) Molecular structures of achiral luminophores TPE, 2,3,5,6‐tetrakis(4‐methoxyphenyl)pyrazine (TPP‐4M), and 9,10‐bis(phenylethynyl)anthracene (BPEA). (c) Schematic illustration of the hierarchical self‐assembly and co‐assembly processes.

      Source: Reproduced with permission [55]. Copyright 2019, American Chemical Society.

      The development of chiral AIE‐based supramolecular systems greatly improved the CPL performance and expanded the family of AICPL materials. Besides, the properties of the resulting CPL‐active materials were highly tunable via modulation of the supramolecular interactions.

2.6 Polymers

Compared to the small molecule and supramolecular systems, polymers possess distinctive advantages, such as highly stable and readily processible. In 2013, Zhu et al. prepared the first conjugated polymer 69 with AICPL by incorporating difunctional TPE units and tyrosine‐derived pendants via Sonogashira reaction (Figure 2.24) [57]. The resulting polymer was nearly nonemissive in a THF solution, but appeared to be strongly luminescent upon the addition of water, indicating a typical AIE feature. It revealed obvious CPL around 500 nm both in solution and in the aggregated state, and the g_lum can be tuned from +0.08 to +0.44 by changing the content of water.

Figure 2.24 (a) Molecular structure of chiral TPE‐containing polymer 69 and corresponding g_lum. (b) Plot of (I/I₀) values versus water fraction of polymer 69 in THF/H₂O mixtures (1.0 × 10⁻⁵ M). (c) CPL dissymmetry factor g_lum versus water fraction of polymer 69 in THF/H₂O mixtures (1.0 × 10⁻⁵ M).

      Source: Reproduced with permission [57]. Copyright 2013, The Royal Society of Chemistry.

In 2015, Zhu and coworkers synthesized a series of chiral conjugated polymers (70–73) with AIE activity via Sonogashira and Suzuki reactions (Figure 2.25) [58]. R‐1,1′‐binaphthyl group and the TPE unit were introduced into the main chain as chiral moiety and AIE‐active moiety, respectively. The chiral conjugated polymers 70–73 all showed strong luminescence and obvious CD signals. However, only 70 exhibited detectable CPL signals around 530 nm in the aggregated state with g_lum of −1.6 × 10⁻³. Further morphology characterization showed that polymer 70 formed right‐handed helical nanostructure in the THF/H₂O mixture, which was consistent with the negative CPL signal. In 2018, another two examples of chiral AIE‐active conjugated polymers 74 and 75 were prepared by Cheng et al. via click chemistry and Suzuki cross‐coupling reactions (Figure 2.25) [59, 60]. Polymer 74 exhibited weak luminescence and nearly no CPL signal in a THF solution. When f_w of the THF/H₂O mixture exceeded 40%, AICPL could be easily observed and g_lum reached up to −5.6 × 10⁻³ (around 500 nm) and +7.0 × 10⁻³ (around 500 nm) at f_w = 90% for R‐74 and S‐74, respectively. Polymer 75 exhibited CPL with g_lum of −1.3 × 10⁻³ (496 nm) and +1.1 × 10⁻³ (496 nm) for R‐75 and S‐75, respectively, in the spin‐coated film. R‐75 and S‐75 were also used in doping‐free electroluminescent devices, which showed CPL centered at 505 nm with higher g_EL of −1.9 × 10⁻² and +2.4 × 10⁻², respectively.

Figure 2.25 Molecular structures of AIE‐active chiral conjugated polymers 70–75 and corresponding g_lum [58–60].

In 2017, Cheng et al. reported five three‐component chiral conjugated polymers 76–80 incorporating the binaphthyl, fluorine, and TPE moieties, which functioned as the chiral source, Förster resonance energy transfer (FRET) donor and FRET acceptor, respectively (Figure 2.26) [61]. The polymers showed CPL with |g_lum| of 2.0–4.0 × 10⁻³ (480 nm). In the same year, Cheng et al. prepared two chiral conjugated polymers 81 and 82, which were comprised of four components as well as two FRET pairs (Figure 2.26) [62]. The fluorene moiety