Synthesis Of Multi-functional OPEs Molecular Wires

This thesis is concerned with the design and synthesis of multi-functional OPEs molecular wires.First, we summarized the importance of the molecular electronic devices in nanotechnology and molecular electronics, and the recent development of the synthesis and measurement of molecular electronic devices.In chapter 2, six OPEs molecular wires containing redox benzoquinone group with different lengths were designed: Quinones are frequently found in nature as electron acceptors and can be easily reduced and reoxidized, thus making them ideal for study in molecular electronic devices. Since having the redox benzoquinone group, the six molecules were designed to study the ability of electron transfer, the possibility of switching and data storage. The key step involved the Sonogashira reaction to construct the backbone of the molecules using the convergent strategy. Originally four precursors were quickly synthesized starting from four cheap materials including 1,4-dimethoxybenzene. This synthetic route had to be used in the palladium catalyzed coupling since quinones are known to oxidize Pd (0) to Pd (II), terminating the catalytic cycle. Unluckily, the final oxidation by CAN and PIFA or demethylation by BBr₃ and AlI₃ of dimethoxylphenyl compounds to benzoquinone or hydroquinone derivatives were unsuccessful. This may be due to the instability of the terminal thioacetyl group. After several attempts, a new route for the synthesis of hydroquinone derivatives was proposed and approved successful. Starting from the TBS protected hydroquinone, the alkyne part was synthesized through iodination, Sonogashira coupling and desilylation by treated with K₂CO₃. The first target hydroquinone was accomplished by desilylation by TBAF under low temperature. Besides, the precursor of the second target molecule and the building block for synthesizing the third and fourth hydroquinone were finished. Hydroquinone derivatives could be transformed to benzoquinone through electrochemical oxidation. Benzoquinone could also be transformed to hydroquinone. This route paved the way for synthesizing the other molecular wires and testing their electrical properties.