  Two-dimensional ionic liquids with single site anion and cation-neutral dimer
are studied by computer simulations and integral equation techniques, with the
aim of characterizing differences with single site anion-cation mixtures, and
also with three dimensional equivalents of both models, in order to see the
competition between the Coulomb interactions and the clustering restrictions
due to reduced dimension. We find that the addition of the neutral site to the
cation suppresses the liquid-gas transition which occurs in the case of the
monomeric Coulomb system. Instead, bilayer membrane type ordering is found at
low temperatures. The agreement between the structural correlations predicted
by theory and the simulation is excellent until very close to the no-solution
region predicted by the theory. These findings suggest various relations
between the nature of the clustering at low temperatures, and the inability of
the theory to enter this region
