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David Bradley ISSUE #74
July 2008
Communicating with Logical Chemistry

Alberto Credi of the University of Bologna, Italy, and colleagues have built a simple glowing molecule that can carry out logical operations of the kind used in encoding the data transmitted down fiber-optic cables for voice and internet connections. The work could eventually lead to the development of photonic devices for signal processing and transmission smaller and faster than those currently employed in communications technology. In the short term, molecular logic systems could be used to perform relatively simple computing tasks that, however, cannot be accomplished with silicon-based devices,e.g., in nanoscale spaces or living things.

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"We have demonstrated that a glowing fluorophore molecule as simple as 8-methoxyquinoline (just one synthetic step from the commercially available 8-hydroxyquinoline) can be used to implement both 2:1 multiplexer (MUX) and 1:2 demultiplexer (DEMUX) functions," Credi told Reactive Reports. "The molecule exploits the proton-driven reversible modulation of two complementary absorption and fluorescence signals."

The MUX and DEMUX functions are very important ones in information and communication technology. A multiplexer allows the encoding of multiple data streams into a single data line for transmission, and a demultiplexer then decodes such entangled data streams for the single signal at the receiving end. There are very few examples of molecules that can perform as a 2:1 MUX or as a 1:2 DEMUX. However, these systems usually rely on carefully designed multicomponent molecules and coupling to an external optical device, or suffer from the problem of being dependent on the state of the input address, which makes them too complex to work with.

"Although the purpose of our study was not to produce a practical device," explains Credi, "we investigated the reversibility of the acid-base switching process and we showed that such a process takes place also when the fluorophore is embedded in a polymer film." This suggests that the compound could ultimately be embedded into a practical device that could be connected to a system.

"We think that the important message of this work is the demonstration that a structurally simple molecule can perform a complex function," adds Credi. "Indeed, the identification of structurally simple but functionally valuable molecules is an important task in nanoscience. Species of this kind can be synthesized cheaply and in large amounts, thereby enabling a wide range of experimental investigations, such as ones carried out in diverse environments or with unconventional techniques, and fostering potential applications."

Angew Chem, 2008 (in press)