Centrally Coordinated Cobalt Porphyrin Monolayers on the Surface of TiO2 Nanoparticles

Aminopropyltrimethoxysilane (APTS) on the surface of TiO2 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 TiO2, 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 TiO2-APTS-CoTAPPI assembly were calculated with the molecular mechanics approach (MM2).