PRERESONANCE RAMAN EFFECT OF SOME CROCONATES IN THE SOLID-STATE

The optical and Raman spectra of several salts of croconic acid were i nvestigated in order to obtain a better understanding of solid-state e ffects. The results indicate that for the sodium and barium salts the perturbations can be ascribed to a decrease in the local symmetry of t he anion. On the other hand, for the thallium and silver salts the per turbations are much more dramatic, clearly indicating the presence of charge-transfer effects. For the silver salt, the abnormal enhancement in the Raman spectrum is ascribed to the presence of silver micropart icles in the surface of the solid.