Synthesis of porphyrin-introduced silica gels by sol-gel process.

Using a hydroxyl group appended free base porphyrin derivative (HP), porphyrin-introduced silica gels were synthesized by a sol-gel process. The HP content in the materials linearly increased with increasing the HP concentration. Meanwhile, free base tetraphenylporphyrin (TPP) with no hydroxyl groups were almost not incorporated into the silica gels. These facts suggested that the interaction between hydroxyl groups of the HP molecules and silica network is considerably strong. The UV-vis characters of HP-introduced materials were almost the same as pure HP molecules. The Beer's plot indicated that the HP molecules in the materials are dispersed.

Incorporation of porphyrins into mesopores of MCM-41.

To introduce porphyrins such as the alcoholic-hydroxyl-group-appended free base porphyrin derivative (HP) of 5-[4-(3-hydroxylpropyloxycabonyl)phenyl]-10,15,20-triphenylphorphine into mesopores of MCM-41, samples were treated with 0-4.0 mmol dm-3 HP toluene solutions and the materials obtained were characterized by various means. The framework structure of MCM-41 was not altered by the treatment. With increasing HP concentration, the specific surface area and pore size decreased; in contrast, the number of HP molecules in the material increased almost linearly from 0 to 0.17 groups nm-2. These facts reveal that the HP molecules are incorporated into mesopores of MCM-41. IR results indicated that the hydroxyl group of the HP molecule reacts with surface free SiOH groups of the MCM-41 by a dehydration reaction. Diffuse reflection UV-vis spectra of the HP-introduced material were almost the same as that of pure HP molecules. The Beers plot suggested that the HP molecules in the material are dispersed at an HP concentration less than 1.0 mmol dm-3, and above that concentration, aggregation or flattening of the HP molecules on the MCM-41 surface takes place.