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Our current research can be categorized as follows:

1) Develop new synthetic methods and studies of interesting molecular structures.
　Zinc dust in aqueous ammonia was commonly employed in the reduction of anthraquinone derivatives to their corresponding anthracenes or anthracenones, which are important remedies for the treatment of skin psoriasis. However, it is not very easy to control the extent and the regiochemistry of the reduction. To circumvent the problems, we develop a new method, which can effectively reduce anthraquinones to anthracenones in regioselective fashion. Moreover, we provide a rationale for the formation of the bianthracenones frequently evidenced in the reduction as major byproducts. Many interesting structural features were observed in bianthracenones. Their crystal structures show that the compounds adopt gauche comforamtions, viewing along the carbon-carbon bond connecting two anthracenone units, as the most stable form at the solid state. Low temperature dynamic NMR studies support the same structural properties. To understand the origin of the preference for the gauche form, high level of theoretical calculation was performed.
　The results indicate that both of steric and electronic effects contribute to the observed conformations.

Figure 1. (A)Chemical structure (B) Nnewman projection and X-ray structure of bianthracenone.

2) Develop new organic light emitting materials based on Coumarin Derivatives
　Molecular aggregation is one of key causes leading to the failure of organic light emitting diodes (OLED). To this regard, we designed and synthesized new series of fluorescent molecules, which either can form nice glassy film or exhibit high fluorescent even at solid states. The red fluorescent compounds have been fabricated to devices for evaluating their emitting efficiency and the purity of color.

Figure 2. Fluorescence emission images of improved coumarin derivatives (right for each set) vs their counterparts (left for each set).

　Studies show that the compound can form a smooth single layer and emit pure red light (CIE = 0.63, 0.35) with 0.1% efficiency. Comparing to the existing data on the red emitter, our compounds show great promise in the application of OLED.

3) Develop fluorosensors selectively for lead ions
　Detection of lead ions is important in the areas of environmental protection and biological functions. However, the development of fluorosensors for detrimental metals, especially Pb(II), has lagged behind due to the special nature of this metal such as energy-orbital coupling. We have designed and synthesized coumarin-azacrown hybrid for selective recognition of Pb(II). Among 15 metal salts investigated in our studies, our fluorosensors exhibit unprecedented selectivity towards Pb(II). Moreover, recognition event can be visualized by naked eyes without the assistance of advanced optical instruments.

Figure 3. Visual fluorescence emission observed by the recognition of Pb2+ ion by our fluoroscent chemosensor.

4) Develop fluorosensors for carbohydrate binding proteins
　Glycoproteins are involved in many important biological events such as immune defense systems, proliferation and signal transduction etc. This type of proteins normally resides at cell surfaces and possesses carbohydrate binding sites. Overproduction or mutation of the proteins results in severe health problems. It is worthwhile developing diagnostic agents for the detection of these proteins quantitatively. As part of our chemosensors program, new fluorosensor aiming to recognize carbohydrate proteins was prepared based on a coumarin dye and glucose derivatives. Our studies show that the fluorosensor can signal the presence of the targeted protein by changing the fluorescence intensity.

Figure 4. Visual fluorescence emission observed by the recognition of Con A by our fluoroscent chemosensor.

5) Develop fluorescent probes to study structural features of new enzymes related to antibiotics-resistance problems
　Antibiotics-resistance has become a serious problem at the turn of new century because bacteria have learned how to dodge the action of antibiotics, which used to be very effective against bacteria infection. New enzymes have been produced in bacteria to meet the needs. In order to design new antibiotics to inhibit the functions of these new enzymes, it is necessary to understand the structural features of these new enzymes, especially the active site. In collaboration with Dr. Liang, Po-Huang at institute of biological chemistry, academia sinica, our group has synthesized few FPP analogues to characterize enzyme's activities. New generations of substrates with fluorophores incorporated were developed and used to probe the conformational change during catalysis. We are now able to calculate rate constants for each step during catalysis taking advantage of the fluorescence change of the fluorescent probe. No isotope labeling is required to monitor the progress of the reaction. In addition to the studies of kinetics, these new fluorescent probes will be applied in the field of proteomics for effectively screening new pyrophosphatases in the future.

Figure 5. Fluorescence emission quenching was observed once the substrate equipped with a fluorophore was bound to UPPS.

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