Hermann Wegner and Luca Schweighauser, University of Basel, Switzerland, have made the surprising discovery that the cyclotetraazocarbazole they prepared is multichromic. The molecule changes from yellow to green in chlorinated solvents when irradiated with UV light and the process is dependent on temperature. The same change was observed with a switch between acidic and basic conditions.
The team have exploited this behavior to build various integrated logic gates, including an OR, NOT and an AND function. The use of molecular logic units hints at the future development of computers that use chemical changes rather than shuffling electrons around semiconductor circuits. However, such logic gates might also be used today in smart sensors and diagnostics.