The international team, led by researchers from the IBM research laboratory in Zurich, Switzerland, has developed a method for managing the selectivity of chemical reactions, based on reversible and selective formation and dissociation of atomic links caused by the tip of the tunnel microscope, which can not only trigger chemical reactions with unprecedented spatial and temporal resolution, but also open up new reactions.
To create complex molecules or molecular machines, a set of atoms has to be assembled together and connected in a precise way. This involves mixing reagents, possibly stimulating reaction through a catalyst, and then extracting products with varying degrees of efficiency. What if simple molecules and chemical connections could be controlled if you wanted to? This is the ultimate goal of the Moldam project launched by IBM Research two years ago.
Specifically, this involves creating "individual" matter from individual atoms by managing chemical reactions with the tip of a scanning microscope. Using super-speed light pulses, scientists have observed how connections are formed and atoms are re-engineered during a chemical reaction. Now, by applying a certain voltage to atomic connections, Dr. Florian Albrecht of IBM Research Europe and its co-authors have been able to create three different products from the same molecule.
Three new molecules made of one
Selectivity and chemical responses can be improved by regulating certain parameters or regulating available proton donors — thus influencing the way atoms exchange electrons to form connections. "," researchers point out in their own.
So they decided to control the formation of atomic bonds in a completely different way, and first they synthesized the molecule 5.6, 11,12-carbontetracene, and they removed the chlorine atoms, thus severing the four C-Cl and the C-C central bond.
This intervention creates an intermediate molecule containing a diradical, a central ring of 10 carbon atoms, six of which have uncoupled electrons. By applying relatively high voltage, they created a new C-C bond, which led to the formation of a new ring known as a curved alkin; the original molecule then became a new molecule consisting of four rings.
Note that the system is designed so that the remaining uncoupled electrons cannot connect to create another C-C link, as is usually the case. On the other hand, the application of lower voltage to the intermediate molecule led to the formation of a new four-carbon ring inside it called Cyclobutadiene. It would not be possible to obtain these different carbon networks with traditional chemistry.
So the team turned the original molecule into three different products. "," writes Igor Alabugin and Chaouway Hu in an accompanying article. Each of the products produced is capable of performing various chemical functions, e.g. binding for transitional metals or participating in oxidation-remediation reactions. All three can even be used as a logical gate in molecular electronics.
The main advantage of the method is that these reactions can be reversed by the opposite polarity impulses, since each product can be returned to its original state by a new electronic pulse. By forcing one molecule to take different forms by applying exact stresses and currents, researchers can directly monitor electron behaviour and determine the optimal configuration of organic compounds according to the desired result.
It should be noted that this experiment was carried out in cryogenic conditions, a temperature at which atoms and molecules are almost stationary. Reproduction of the method at temperature close to room temperature may be more difficult, and some atomic bonds are more difficult to break.
However, this work opens the way for better control of chemical reactions — at least in some cases.