Surface enhanced Raman scattering and normal coordinate analysis of 1,10-phenanthroline adsorbed on silver sols

The surface enhanced Raman scattering of 1,10-phenanthroline adsorbed on si lver sol has been obtained and analyzed by using normal mode calculations b ased on a valence force field suitably determined for this molecule. Eviden ce has been found for Ag-N bond formation with the silver surface, supporti ng the validity of a chemisorption process. The experimental and calculated data suggest an adsorbate-substrate interaction with perpendicular or tilt ed orientation of the molecule with respect to the colloidal surface. The h alide anion effect on the SER spectrum improves a charge-transfer enhanceme nt process involving adsorbate and metal electronic states. The results obt ained on colloids agree with those detected by measurements performed on si lver electrode. The similarity between SERS and normal Raman spectra of the corresponding 1:2 Ag(I)-phenanthroline complex indicates that the molecule is perturbed upon adsorption as well as upon coordination in the argentous complex.