Abstract
In this work, experimental isotherms of silver on hexahelicene and heptahelicene were collected at five adsorption temperatures using the quartz crystal microbalance strategy. Two analytical models of statistical physics (MMPG and MMRG) were applied to explain the complexation process of the two helicenes. Based on the physical significance of the two models' parameters, the silver adsorption was found to be typical to an endothermic phenomenon by the intermediate of the steric variables. Thus, the fitted values of the adsorbed amounts at saturation (Q(S1) and Q(S2)) were the highest in the case of heptahelicene adsorption. The van der Waals parameters (cohesion pressure a and covolume b) involved in the MMRG model explain the decrease of hexahelicene isotherms at high concentration through the lateral interactions between the adsorbates. Interestingly, the analysis of the complexation energies [|(-E-1)| and |(-E-2)|] indicated the strongest interaction of silver-[7]helicene. The novel clarifications of the physicochemical description of adsorption isotherms indicated that the heptahelicene can form a stable complex with silver ions.