Redox-active self-assembled monolayers(SAMs) on gold are traditional molecular systems for the study of long-range electron transfer process at electrolyte/electrode interfaces,particularly the distance and reorganization dependences.Ferrocene-terminated monolayers(Fc-SAMs) have been extensively studied in the past two decades because of their easy preparation,good reproducibility,and well-defined electrochemistry.The redox behavior of Fc-SAMs is in fact typically non-ideal and influenced by the microenvironment,e.g.,double layer and ion-pairing effects that are associated with both monolayer structure and the electrolyte.In this work,we first examined the redox behavior of single component 11-ferrocenyl-1-undecanethiolate SAMs on gold(FcC11S-Au),and discovered that the two distinct pairs of redox peaks are corresponding to rather moderate differences in the packing densities of the two structural domains.On the basis of the Frumkin isotherm,we have fitted the intermolecular interaction parameters in the two different structural domains of the monolayers,which can be individually modulated by either changing the composition of the monolayer or adding organic solvents to the aqueous electrolyte.With the above "new insights" in the intermolecular interactions in Fc-SAMs,we went ahead to compare "ideally behaved" redox-active self-assembled monolayers on gold prepared from post-assembly exchange and co-adsorption processes,respectively.The different distributions of the redox centers in the binary SAMs,as indicated by the distinct formal potentials and intermolecular repulsions,were explained in terms of their kinetically vs.thermodynamically controlled formation processes.