The effects of increasing size and tetra-methylation over dimerization, electronic and magnetic properties of the pentalene, s-indacene, dicyclopenta-[b,g]-naphthalene and dicyclopenta-[b,i]-anthracene series, were studied. Potential energy surfaces were evaluated using the hybrid-density functionals BHandH and LC-wPBE. Our results suggest a linear scaling of the dimers stabilization and interaction energies. NICS values indicate that, there are no effects over the five member rings antiaromaticity, however the central rings are slightly aromatic for the largest molecules. The presence of methyl groups has a small effect over the reactivity of the molecules, while the increasing of system-size increases the reactivity of the five membered-rings. (C) 2012 Elsevier B.V. All rights reserved.