SURFACE-ENHANCED RESONANCE RAMAN-SPECTRA OF WATER-INSOLUBLE TETRAPHENYLPORPHYRIN AND CHLOROPHYLL-A ON SILVER HYDROSOLS WITH A DIOXANE MOLECULAR SPACER

A surface-enhanced resonance Raman spectroscopic (SERRS) study of tetr aphenylporphyrin (TPP) on a silver hydrosol, obtained by mixing a diox ane solution of the water-insoluble TPP with the hydrosol, indicates t hat there is no metallation of the porphyrin. By contrast, water-solub le porphyrins such as tetra-N-methylpyridylporphyrin (TMPyP) have been shown to undergo metallation, We suggest that the TPP is encapsulated within a dioxane envelope which is co-adsorbed to the surface of the silver hydrosol and functions as a molecular spacer. This spacer does not eliminate the analytical advantages afforded by SERRS, but does pr event significant perturbation from the native conformation, as is dem onstrated by results obtained using chlorophyll a.