D-π-A type carbazole and triphenylamine derivatives with different π-conjugated units: Tunable aggregation-induced emission (AIE) and mechanofluorochromic properties

Synthesis and Performance of Imide-Based Small Molecules Containing Carbazole Groups with AIE Properties

Here, two novel naphthalimide derivatives SNI-Cz and SNI-DCz with AIE were designed and synthesized. The correctness of the two structures was characterized by NMR and HRMS. Their crystal structures, photophysical properties, electrochemical properties, thermal stabilities, fluorescence lifetime and yields have been characterized. Photoluminescence experiments revealed that SNI-DCz had superior properties due to the D-π-A-π-D structure and sliding away stacking of molecules. SNI-DCz exhibited weak fluorescence in pure DMF, with a significant AIE effect observed in the 40% water mixture and a sharp increase in fluorescence intensity was also observed. Cyclic voltammetry and thermogravimetric analysis indicated that SNI-DCz had good electron affinity and thermal stability. The excellent properties of SNI-DCz made it a promising emitter for optoelectronics.

Ni-Catalyzed Asymmetric C-P Cross-Coupling Reaction for the Synthesis of Chiral Heterocyclic Phosphine Oxides

Nickel performs excellently in C-C and C-X cross-coupling reactions. Here, we disclose a Ni(II)-catalyzed asymmetric C-P cross-coupling reaction to afford valuable chiral heterocyclic tertiary phosphine oxides. The method is mild and efficient, which invokes a self-sustained nickel catalytic cycle without an external reductant, light irradiation, or electricity.

Methoxy substituent facilitated wide solvatofluorochromism, white light emission, polymorphism and stimuli-responsive fluorescence switching in donor-π-acceptor

Introducing methoxy substituent into triphenylamine-acetophenone based donor-π-acceptor fluorophore, 3-(4-(diphenylamino)phenyl)-1-phenylprop-2-en-1-one (1), produced strong solvatofluorochromism including white light emission, fluorescent polymorphs and mechano-responsive fluorescence switching. The unsubstituted and methoxy substituted compounds displayed strong solvent polarity mediated tunable emission in the solution. Interestingly, 3-(4-(diphenylamino)phenyl)-1-(4-methoxyphenyl)prop-2-en-1-one (2) and 3-(4-(diphenylamino)-2-methoxyphenyl)-1-(4-methoxyphenyl)prop-2-en-1-one (3) showed single molecule white light emission in DMSO and ethanol, respectively. 1-3 exhibited strong green/yellow fluorescence in the solid-state (Quantum yield (Φ_f) = 10 to 23%). 2 produced fluorescent polymorphs (green (2-G) and yellow (2-Y). Single crystal structural analysis revealed that donor and acceptor phenyl units adopted coplanar conformation in 2-G and 3 whereas twisted molecular conformation in 1 and 2-Y. Further, 2-G exhibited π…π interactions facilitated isolated dimers whereas 2-Y showed well separated molecules in the crystal lattice. Aggregation induced emission (AIE) studies showed morphological transformation induced fluorescence tuning for 2. The intramolecular charge transfer (ICT) from TPA to acetophenone was confirmed by computational studies. Mechanofluorochromic (MFC) studies of 1 showed only slight reduction of intensity without modulating fluorescence wavelength significantly but 2 and 3 exhibited visible emissive colour change from yellow to green and vice versa by crushing and heating. Both 2 and 3 also exhibited self-reversible fluorescence switching that was confirmed by PXRD pattern. Thus, methoxy group introduction resulted in obtaining white light emitting fluorescence molecules in the solution state and self-reversible fluorescence switching materials.

A Novel Bifunctional Nanoplatform with Aggregation-Induced Emission Property for Efficient Photodynamic Killing of Bacteria and Wound Healing

BACKGROUND

Photodynamic antimicrobial therapy (PDAT) has been extensively studied because of its potential applications such as precise controllability, high spatiotemporal accuracy, and non-invasiveness. More importantly, it is difficult for bacteria to develop resistance to the aforementioned PDATs. However, the selectivity of traditional PDAT methods to bacteria is generally poor, so it has been proposed to introduce positively charged components such as quaternary ammonium salts to enhance the targeting of bacteria; however, they always possess high toxicity to normal cells. As a result, measures should be taken to enhance the targeting of bacteria and avoid side effects on normal cells.

METHODS AND RESULTS

In our work, we creatively design a nanoplatform with high anti-bacterial efficiency, low side effects and its size is approximately 121 nm. BSA, as a nanocarrier, encapsulates the photosensitizer (E)-4-(4-(diphenylamino)styryl)-1-methylpyridin-1-ium with AIE properties named as BSA-Tpy, which increases its circulation time in vivo and improves the biocompatibility. Under acidic conditions (pH = 5.0), the surface positive charge of the BSA-Tpy is increased to +18.8 mV due to protonation of amine residues to achieve the targeting effect on bacteria. Besides, under the irradiation of white light, the BSA-Tpy will produce ROS to kill bacteria efficiently about 99.99% for both Gram-positive and Gram-negative bacteria, which shows the potential application value for the treatment of infected wounds.

CONCLUSION

We have developed a feasible method for photodynamic antibacterial therapy, possessing excellent biocompatibility and high antibacterial efficiency with good fluorescence imaging property.