Spectroscopic Analysis of Adsorbed Macrocyclic Complexes on Ceramic and Related Materials

Abstract

Various spectroscopic methods have been used to investigate the interaction of ceramics and related materials with porphyrins and catechols. Our particular interest, in addition to the chemistry of these compounds, was to determine the commutative properties of the Clay – Macrocyclic system. Attempts have been made to use the clay environment in the role of a catalyst on which to perform a number of reactions with these compounds. These reactions can usually only be carried out in homogeneous solutions. One such reaction is the preparation of a porphyrin on the clay. This is shown to occur readily at low temperature compared to solution methods. Such porphyrin compounds are of fundamental interest in understanding nature's catalyst. The reaction of pyrrole and a group of different aldehydes in the presence of cation – exchanged clays resulted in the formation of an intermediate porphyrin which then oxidized to porphyrin. These intermediates formed in the interlamellar and on the surface of montmorillonite, but only on the surface of the kaolinite. When the free bases TNPH2 and TTPH2 were adsorbed on the montmorillonite, the process resulted in the formation of their dications, in the presence of cations like Fe(III). Formation of metalloporphyrin was observed in the presence of cations like Cu(II) in the exchanged sites. The reaction of the water soluble porphyrin TPPS with the cation – exchanged montmorillonite and kaolinite resulted in the formation of metalloporphyrin containing the following cations: Fe(II), Fe(III), Cu(II), Co(II), Ni(II), Zn(II), Cd(II), Sn(IV) and UO2+. The stability of these and some Fe(III) and Sn(IV) metalloporphyrin on clays was investigated. Another type of complex was formed when Fe(III)PPIX reacted with the cation – exchanged montmorillonite. In these complexes the cation binds to the porphyrin via the propionic carboxylate group. The adsorption of phthalocyanines on montmorillonite produced different coloured phases after heat treatment. These complexes were found to be intercalated only after heating the powdered samples.Firing montmorillonite and vermiculite clays was studied by means of Mössbauer and photoacoustic spectroscopy. Reduction of montmorillonite with catechols and some other hydroxybenzene reducing agents, by electron transfer from these ligands to the active sites on montmorillonite have also been studied. The reduced montmorillonite showed different behaviour to that of the original sample on firing