Molecular Species Disturbing the Fluid–Solid Phase Transition of Nitrogen Adsorbed on Graphite: Importance of Aromaticity

The fluid-solid (FS) phase transition of N2 adsorbed on graphite is known to be depressed abnormally by conjugated coplanar molecules such as benzene and copper phthalocyanine. This paper describes an investigation of the influence of a non-aromatic conjugated species (1,3-butadiene), a non-aromatic cation acceptor (18-crown-6), a strong electron donor (tetrathiafulvalene) and a strong electron acceptor (tetracyanoquinodimethane) on the FS phase transition of N2, when they were preplated on graphite. These species were, in fact, found to have no significant effect. This implies that molecular properties such as cation acceptance and electron transfer are of no importance, whereas the aromaticity of co-existing species plays a crucial role in disturbing the phase behaviour of N2.