Xie Han

Fluorene-based novel gold(I) complexes with aggregation-induced emission (AIE) or aggregate fluorescence change characteristics: from green to white emission

In this paper, five fluorene-based gold(I) complexes are synthesized and characterized. They exhibit typical aggregation-induced emission (AIE) properties or significant aggregate fluorescence change behaviors. Their thin-film and solid state fluorescence spectra are consistent with the luminescence of all luminogens in DMF–H2O mixtures with high water content. The emission color changes with different numbers of fluorene units. Among them, it is remarkable that luminogens 4 and 5 emit a bright white light in the thin-film and solid state. In addition, their thin-film absolute fluorescence quantum yields are also investigated. The results indicate the luminogen 4 gold(I) complex, with three fluorene units, exhibits the highest thin-film emission quantum yield, which is up to 65.42%.

1,8-Naphthalimide-based highly blue-emissive fluorophore induced by a bromine atom: reversible thermochromism and vapochromism characteristics

We report a structurally simple 1,8-naphthalimide-based fluorescent molecule. Its solid shows an intense blue emission with an absolute fluorescence quantum yield of up to 82.33%. The novel luminogen exhibits reversible thermochromism and vapochromism behaviors.

Aggregation-induced emission behavior of a pH-controlled molecular shuttle based on a tetraphenylethene moiety

Tetraphenylethene (TPE) with aggregation-induced emission (AIE) behavior as a popular backbone is applied widely in the construction of functional supramolecular systems. In this work, a TPE-based linear molecule having amide and amine units is synthesized. Its ammonium template is used to construct the N-hetero crown ether-based [2]rotaxane by the template-directed clipping approach. Their structures are well-characterized by NMR, MALDI-TOF-MS and elemental analysis. Owing to the existence of the amide unit, [2]rotaxane possesses the function of a molecular shuttle. The shuttling motion of the macrocycle component between the ammonium station and the amide station can be driven by external acid-base stimuli in solution, accompanied by changes in visual behavior. Investigation on their AIE behavior shows that (1) ammonium reaches the aggregation state almost in the presence of same water with the deprotonated form of ammonium; (2) the [2]rotaxane that the macrocycle component locates at the site of ammonium forms the aggregation state in the presence of less water than the deprotonated [2]rotaxane that the macrocycle component locates at the site of the amide, attributed to stronger interaction between the crown ether component and the TPE unit of the template component when the distance between the two is shorter. The result indicates that the shuttling motion of the macrocycle component can adjust the aggregation state of AIE molecules.

A hemicyanine-based colorimetric and ratiometric fluorescent probe for selective detection of cysteine and bioimaging in living cell

A new ratiometric fluorescent probe based on a hemicyanine dye was synthesized. Investigation on the response behavior towards amino acids showed that the probe had a capability of rapidly and selectively detecting cysteine over other biothiols such as glutathione and homocysteine with similar structure and reactivity, and it also displayed a high selectivity and rapid response. Moreover, the probe had good water solubility, which authorized it could be applied in fluorescent bioimaging. The laser confocal fluorescence images indicated that the probe could visualize the intracellular cysteine. This work suggested that it could be utilized as a fluorescent indicator to discriminate the endogenous cysteine in living cells.

Synthesis of rotaxanes and catenanes using an imine clipping reaction

Supramolecular chemistry and self-assembly provide a valuable chance to understand the complicated topological structures on a molecular level. Two types of classical mechanically interlocked molecules, rotaxanes and catenanes, possess non-covalent mechanical bonds and have attracted more attention not only in supramolecular chemistry but also in the fields of materials science, nanotechnology and bioscience. In the past decades, the template-directed clipping reaction based on imine chemistry has become one of the most efficient methods for the construction of functionalized rotaxanes and catenanes. In this review, we outlined the main progress of rotaxanes and catenanes using the template-directed clipping approach of imine chemistry. The review contains the novel topological structures of rotaxanes and catenanes, functions and applications.

Photoactivatable fluorescence enhanced behaviour of benzo[c][1,2,5]oxadiazole-dressing tetraphenylethene

A photoactivatable benzo[c][1,2,5]oxadiazole-dressing tetraphenylethylene (TPE) was developed. The optical performance results indicate that UV-irradiation can lead to remarkable emission enhancement in solution states due to the cyclization of the TPE component. Application in the solid state confirmed that it has a potential to serve as a photoactivatable visualized material.