The size-specific influence of alkali metal ions in the gradual transition from cluster rearrangement to solvation dynamics is investigated by means of molecular dynamics simulations for alkali metal cation-hexafluorobenzene systems, M+-C6F6 (M = Na, K, Rb and Cs), surrounded by Ar atoms. To analyze such transition, different small aggregates of the M+-C6F6-Ar-n (n = 1, ..., 30) type and M+-C6F6 clusters solvated by about 500 Ar atoms are considered. The Ar-C6F6 interaction contribution has been described using two different formalisms, based on the interaction decomposition in atom-bond and in atom-effective atom terms, which have been applied to study the small aggregates and to investigate the Ar solvated M+-C6F6 clusters, respectively. The selectivity of the promoted phenomena from the M+ ion size and their dependence from the number of Ar atoms is characterized.