The stepwise binding energies (Delta H degrees(n-1,n)) of 1-4 HCN molecules to the phenylacetylene radical cation (C8H6 center dot+) are determined by equilibrium thermochemical measurements. The binding energy (10.5 +/- 1 kcal/mol) of the C8H6 center dot+ (HCN) complex is dominated by the ionic hydrogen bonding interaction (ph-C CH delta+center dot center dot center dot NCH). For higher clusters, the attachment of HCN molecules occurs through two comparable interactions involving the association of HCN molecules (ph-C CH delta+center dot center dot center dot NCH center dot center dot center dot NCH center dot center dot center dot) to form a linear hydrogen bonding chain or the interaction with the ring hydrogen atoms through hydrogen bonding (> CH delta+center dot center dot center dot NCH) and bifurcated charge-dipole structures. An interesting pattern of the assembly of linear hydrogen bonded chains is observed and could result in the formation of molecular wires of nanometer length scale. (C) 2012 Elsevier B.V. All rights reserved.