Meijiao Cao

Visible-Light-Dependent Photocyclization: Design, Synthesis, and Properties of a Cyanine-Based Dithienylethene.

A cyanine-based dithienylethene is developed. Its photoisomerization shows that (1) the irradiation of visible light can induce cyclization while the cycloreversion takes place upon irradiation with UV light and (2) the addition of CN(-) can lead to cyclization and cycloreversion upon irradiation of UV light and visible light, respectively.

A dansyl-based fluorescent probe for selectively detecting Cu2+ and imaging in living cells

Copper is a crucial transition metal ion that plays an essential role in environmental, biological, and chemical systems. Therefore an efficient method for detection of copper ions is significant. In this work, a sulfonamide-based probe containing a dansyl fluorophore was synthesized in good yield. This probe exhibited good selectivity and sensitivity for copper ions in aqueous solution without any interference from other metal ions. And it displayed a very low detection limit (2.91 × 10−8 M) for Cu2+, which supported its further application in bioimaging. Its good water-solubility, bio-compatibility and cell permeability leads it to be employed as an efficient biomarker to monitor the level of Cu2+ in living cells. The binding model between fluorescent probe and Cu2+ was evaluated by density functional theory calculations.

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.

Cyanine-based dithienylethenes: synthesis, characterization, photochromism and biological imaging in living cells

Photochromic materials have been widely used in many fields such as electro-optical functional materials and novel bio-materials. In this study, six cyanine-based dithienylethene compounds were successfully developed, and their photoisomerization and emission change properties were fully investigated. The results indicated that the UV/vis absorption of pyridinium-based compounds displayed near-infrared absorption, while their fluorescence showed quenching emission as a result of the changes in structure from open-ring isomers to closed-ring isomers. Therefore these cyanine-based compounds could be applied not only in photochromic materials, but also they could be used as fluorescence switches. Accordingly, one of these compounds was successfully used in the biological imaging of living cells. These results suggest that cyanine-based dithienylethenes may be used as photoswitchable bio-materials in the future.