Photophysical Properties and Adsorption Behaviors of Novel Tri-Cationic Boron(III) Subporphyrin on Anionic Clay Surface

Two types of +3-charged subporphyrin derivatives with m- and p-methylpyridinium as the meso-aryl substituents were designed and synthesized. Their photophysical properties with and without anionic saponite clay were investigated. These cationic subporphyrins were suitably designed for adsorption on the saponite nanosheet surface with their photoactivity. Absorption and emission spectra of these subporphyrin-saponite complexes exhibited strong bathochromic shifts due to the flattening of the molecules on the nanosheet. This behavior was observed as drastic visual changes in their luminescence colors. Additionally, aggregation behaviors were not observed in the saponite complexes even at high dye loading levels for both subporphyrins. Moreover, under such condition, their fluorescence properties on the saponite surface were not only maintained but also enhanced without unexpected deactivations despite the dye molecules are densely introduced on the solid surface. These findings are beneficial for applications of the dye-clay complexes to photofunctional materials such as strongly luminescent materials, highly sensitive clay sensors and artificial photosynthesis systems.