Surface‐enhanced resonance Raman scattering study of the groove binding dye hoechst 33258

The groove binding dye Hoechst 33258 was investigated both in aqueous solution and in the adsorbed form on silver colloids and island films. Fourier transform Raman, resonance Raman and surface enhanced resonance Raman spectra were used together with the results of a normal coordinate analysis for a comprehensive assignment of the rich vibrational spectrum. Relative band intensities in the SERRS spectra indicate that the molecule is adsorbed with its long axis oriented along the silver surface and with the planes of the benzimidazole rings approximately parallel to the surface. The molecule is bound to the surface as a cation protonated at a piperazine nitrogen atom and is desorbed on complete deprotonation.