Adsorption of the Meso-Tetra-p-Tolylporphyrin (TTPH2) and Meso-Tetra-Naphthylporphyrin (TNPH2) onto Montmorillonite

Abstract

The behavior of two porphyrin compounds, meso-tetra-p-tolylporphyrin (TTPH2) and meso-tetra-naphthylporphyrin (TNPH2) was studied and monitored during their adsorption on cation-exchanged montmorillonite clay (MMT). When these two compounds were reacted with MMT, the visible absorption spectra showed a clear shift of 10 nm higher than that found in the acetic acid solution. This suggests that the two compounds prefer to be more planar on the clay surface and, in the case of TTPH2, in the MMT interlamellar layers. The basal spacing of the MMT was increased by 4.4 Å when the TTPH42+ cations entered the spacers. The metal-exchanged ion in the clay is incorporated into the porphyrin rings when the TTPH2 and TNPH2 molecules react with MMT saturated with the metal ion of an appropriate size to fit in the porphyrin ring, such as Cu(II). The process occurred when executed in a solvent miscible with water that allowed the penetration of the hydrated sphere of the metal ion. Metalloporphyrin complexes are formed as a result of this process. The reactions were monitored using visible absorption spectra, diffuse reflectance spectra, x-ray diffraction, infrared spectra, and electron microscopy.