Synthesis and photophysical properties of silica-gel-supported photofunctional (phthalocyaninato)silicon complexes

The photophysical properties and surface structures of silica-gel-supported photofunctional (phthalocyaninato) silicon complexes (SiPC-SiO2) were investigated in terms of their electronic absorption, fluorescence, singlet-oxygen luminescence, and nitrogen adsorption/desorption isotherms. The nitrogen/desorption isotherms indicate that the planes of Sipcs Aanchored by axial ligands are parallel to the silica gel surface. In the proposed structure the tetradentate Pc ligands are considered to coordinate with the silica gel particles, since central elements of SiPcs, such as Si-O-Si-OH, are similar to constituents of silica gel. It was shown that the addition of an organic solvent (chloroform, cyclohexane, etc.), whose refractive index is comparable to that of the silica gels, increases the transparency of the silica gels. This method of adding the solvent allows to quantitatively analyze the photophysical properties and is useful for investigating other modified silicas. The intensities of fluorescence and singletoxygen luminescence decrease with an increase in the amount of SiPcs due to interactions between the SiPcs in aggregates. By changing the amount of SiPcs, solid materials were prepared based on Pc complexes with both monomeric photophysical properties and a high ability for singlet-oxygen generation. The electronic absorption spectra of SiPcSiO2 indicate that a wide optical window is maintained between the Soret and Q absorption bands, even for high concentrations of SiPcs ([SipC] approximate to 10(-2) M). This results in deep-green solids, which is unlike the blue color of the crystals or concentrated solutions (>10(-5) M) of SiPc(OH)(2), ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).