Cyclic voltammetry and FTIR spectroscopy were used to study the structural effects on the electrochemical and spectral properties of the asymmetric alkyl viologen, N-ethyl-N'-octadecyl viologen (1) on bare and n-alkanethiol (CH3(CH2)(n)SH)-coated Au electrodes. The self-assembled monolayers (SAMs) of 1 on the Au electrode showed multiple redox peak for the first reduction of 1 in aqueous 0.1 M NH4PF6 solution. When the assembly of 1 was inserted into monolayers of n-alkanethiols of n > 11, no redox response was observed in 0.1 M NH4PF6. On the other hand, when the alkyl chain length of thiol decreased from n = 11 to 5, the reduction peak potential of 1 shifted to less negative potential. Moreover, the redox reaction of 1 on n-alkanethiol monolayers of n <11 was found to be very slow in the presence of PF6- ion, but to be fast in the presence of other supporting electrolytes (typically Cl-, SO42-and ClO4- ions). The Gamma (ox)/Gamma (red) ratio increases when the alkyl chain length (m) of viologen decreased from m = 18 to 16, 14 and 12. The monomer-dimer FTIR spectral features were observed for the SAM of 1 on the bare An electrode in the presence of PF6- ion, whereas only monomer spectral features were observed on the n-hexanethiol (HT)-coated electrode. It is suggested that the redox moiety of 1 was less compact on a bare Au electrode and the entry of more water molecules into the monolayer strongly favors the dimerization. On the other hand, on the HT-coated electrode, the redox moiety of 1 was more compact than on the bare An electrode and showed monomer spectral features.