Self-assembled monolayers (SAMs) of n-alkanethiol (CH3(CH2)(n)SH, n = 3-17)-coated electrodes have been used to stabilize the assemblies of N-ethyl-N＇-tetradecylviologen (I) and N-ethyl-N＇-dodecylviologen (2) on the electrode surface. The odor behavior of 1 and 2 on the bare Au electrode was unstable because of the weak adsorption of their assemblies on the Au electrode surface. On the other hand, both 1 and 2 are strongly confined and compact in the SAM domain of alkanethiol and showed a stable redox response. The compactness of the assemblies of I and 2 on alkanethiol-coated electrodes can be understood from its blocking effect on the redox reaction of [Ru(NH3)(6)](2+/3+) and EQCM measurements. EQCM measurements demonstrated that the ingress of water molecules into the assembly of 1 and 2 was markedly suppressed at the assembly of 1 and 2 bound to alkanethiol-coated electrodes. Furthermore, the redox behavior of 1 and 2 on the bare and alkanethiols-coated electrodes was also studied in the presence of weakly hydrated anions of ClO4- and PF6-. For the ClO4- ion, an additional oxidation peak was observed for the first reduction of 1 and 2 along with a usual redox wave. While, in the presence of PF6- ions, the electrochemical behavior was largely dependent on the alkyl chain length of thiol. Two redox waves were observed on short chain thiol (n = 3)-coated electrode whereas a single redox wave was observed on the electrodes coated with alkanethiols of n = 5, 7 and 9. An irreversible redox response was observed on the longer alkyl chain (n > 9) thiol-coated electrodes. The observed irreversible response has been attributed to the effective blocking of water molecules at the assembly of 1 and 2 on the long chain alkanethiol-coated electrodes in the presence of weakly hydrated PF6- ions. At these electrodes, 1 and 2 may form an insoluble salt with PF6-ion and are electroinactive. When the same electrodes were transferred to solutions of Cl- or ClO4- ions, the PF6- ions could be readily exchanged with Cl- or ClO4- ions and 1 and 2 became electroactive. Such a situation may not arise at the assembly of 1 and 2 bound to short chain thiol (n < 9) coated-electrodes because of the free how of water molecules into the disordered monolayers of short chain thiols.