It has been known for a long time that the loss of aromaticity of gaseous molecules leads to a large increase of the enthalpy and to a tiny increase of the entropy. Generally, the calculated transition temperature from an aromatic structure towards a non-aromatic structure at which these two contributions cancel is very high. The entropy associated to the loss of aromaticity of adsorbed molecules, such as pyridine on Si(100) and on Ge(100), is roughly the same while the associated enthalpy is much smaller, a consequence of which is a low transition temperature. This allows us to imagine monomolecular devices, such as thermal switches, based on the difference of electrical conductivity between aromatic and non-aromatic species adsorbed on Si(100) or on Ge(100).
['Romain Coustel', 'S. Carniato', 'Gérard Boureau']
A Possible Application of the Contribution of Aromaticity to Entropy: Thermal Switch