Composites with photosensitive 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin entrapped into silica gels

Photosensitive cationic 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin (TMPyP) was entrapped into microporous silica gels prepared by sol–gel method from tetrakis(2-hydroxyethoxy)silane (THES) and tetramethoxysilane (TMOS), resp., using different water and PEG 600 contents in the initial mixture. The absorption spectra of both composites showed that incorporation of TMPyP has led to a bathochomic shift (ca. 8 nm) of the Soret band and to a decrease in their molar absorption coefficient compared to TMPyP in solution. The TMPyP encapsulation kept the molecular state of the porphyrin in the free-base monomer form. In comparison to TMOS analogs, THES composites showed prolonged shape stability at least for 3 months, one-order higher rate of chemical substrate photooxidation and higher photobiocidal activity against E. coli.