The effects of the cation exchange capacity and interlamellar cation identity of smectite clays on the visible spectra of porphyrins.

摘要

A porphyrin, 5,10,15,20-tetrakis(1-methyl-4-pyridyl)-21H,23 H-porphine (TMPyP), was intercalated with montmorillonite clay suspensions to investigate the changes in the visible spectra. This porphyrin was used because it is both positively charged and a free base, meaning intercalation is a result of substituent charges and not coordinated metal ions.; Ultraviolet visible spectroscopy was used to determine the effects of the cation exchange capacity and interlamellar cation identity of a clay on porphyrin. As a result of this interaction, the Soret band and the Q bands were red shifted in solution. The red shift in the Soret band indicates a protonation of the porphin core, while a change in the intensity ratio of the Q bands provides some information as to the orientation of the porphyrin in the interlamellar region.; From the analysis of the Soret band, it was determined that the hydration sphere of the cation as well as the cation exchange capacity of a clay had an effect on the time required to protonate the porphyrin. From the analysis of the Q bands, it was determined that the identity of the cation has some effect on the orientation of the porphyrin. Further research could help in determining the precise orientation of the porphyrin in the interlamellar region of the clay.