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Surface‐EnhancedRaman Spectra of 2‐ and 3‐Hydroxypyridines in Silver Sol
Author(s) -
Mukherjee Kana M.,
Misra T. N.
Publication year - 1996
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/(sici)1097-4555(199608)27:8<595::aid-jrs992>3.0.co;2-a
Subject(s) - tautomer , chemistry , raman spectroscopy , molecule , adsorption , hydrosol , analytical chemistry (journal) , stereochemistry , organic chemistry , optics , physics
Surface‐enhanced Raman spectra of 2‐ and 3‐hydroxypyridines in silver hydrosol were studied. It was observed that 2‐hydroxypyridine exists predominantly as a lactam tautomer in the solid state, in solution and also in the surface‐adsorbed state. However, 3‐hydroxypyridine retains its enolic form i.e. it exists just as pyridinol under all these conditions. The large surface enhancement of the in‐plane vibrations in both cases suggests that the molecules are adsorbed with their planes almost normal to the metal surface. The enhancement factors of the principal Raman bands for both the molecules are inversely related to their Hammett sigma (σ H ) values. The ν max of the new bands which appear on the long‐wavelength side of the electronic absorption band of stable Ag sol on addition of the hydroxypyridines also show an inverse relationship with the σ H values of the molecules. These results suggest that a charge‐transfer mechanism is involved in surface enhancement.