Centrally Coordinated Cobalt Porphyrin Monolayers on the Surface of TiO₂ Nanoparticles

Abstract

Aminopropyltrimethoxysilane (APTS) on the surface of TiO 2 nanoparticles was used to bind cobalt(II) 5,10,15,20-tetra-(4-trimethylaminophenyl)porphyrin iodide (CoTAPPI). The binding involved coordination of amino-group in the APTS to cobalt(II) ion in the center of the porphyrin. The absorption and fluorescence spectra of the products showed that there existed the electron transfer among TiO 2 , APTS, and CoTAPPI. The polarized fluorescence spectra were used to evaluate the coordination constants of the porphyrin and APTS. The molecular geometry and binding energy of the TiO 2 -APTS-CoTAPPI assembly were calculated with the molecular mechanics approach (MM2).