The normal Raman (NR), resonance Raman (RR), surface-enhanced Raman scattering (SERS), and surface-enhanced resonance Raman scattering (SERRS) spectra of the three redox forms of several asymmetric viologens, N-octyl-"-methylviologen (C8MV), N-dodecyl- Nf-methylviologen (C12MV), and N-hexadecyl-Nf-methylviologen (C16MV), have been characterized and compared with the corresponding spectra of the three redox forms of ...