The ‘size matching rule’ in di-, tri-, and tetra-cationic charged porphyrin/synthetic clay complexes: effect of the inter-charge distance and the number of charged sites

Spectral study on the molecular orientation of a tetracationic porphyrin dye on the surface of layered silicates

“…The electrostatic attraction between the dye cation and negatively charged basal oxygen atoms at the silicate surface would lead to a flat orientation of the molecules. Similar arrangement were assumed to occur in other porphyrin/clay mineral systems Eguchi et al, 2004), but the films studied in this work also contained intercalated cations of the surfactant DTMA besides the dye cations. The presence of the surfactant did not significantly alter the arrangement of the dye, taking into account parallel orientation in the systems without a surfactant.…”

Electron transfer reactions in ternary systems on silica gel surfaces: evidence for radical cation diffusion

“…We have demonstrated also that energetics play a role in determining electron transfer rates, and have shown a Marcustype dependence of rate on the free energy for electron 45 transfer 4,14 . In this study we also found evidence for some steric influence on reaction rates.…”

“…40 Note that in this study 9-carboxylic acid anthracene is used since it has been demonstrated to be immobile on the silica gel surface 13 as evidenced by the lack of delayed fluorescence following laser excitation. Hence any dynamic quenching observed is the result of the diffusional characteristics of the 45 co-adsorbed species. The perylene radical cation (530 nm) appears concomitantly with the anthracene radical cation (710 nm) decay.…”

“…Therefore the observed increased rate of electron transfer to perylene observed in the presence of azulene must be ascribable to 40 considerable mobility of the azulene radical cation, where diffusion of the azulene radical to the perylene is faster than diffusion of the perylene to the azulene radical. Even allowing for energetic effects, however, the rate of diffusion of the azulene radical is less than that of the free azulene, since an 45 order of magnitude reduction in the electron transfer rate would not be expected on energetic grounds alone. However, it clearly has a larger diffusion coefficient than perylene demonstrating the complex interaction of parameters which determine difusion rates on silica gel.…”

Activation energies of photoinduced unimolecular, bimolecular and termolecular processes on silica gel surfaces

“…The photochemistry and photophysics of molecules 15 adsorbed on oxide surfaces , contained within zeolites [25][26][27][28][29][30][31][32][33][34][35][36] and porous clays 25,[37][38][39][40] , has been the subject of a number of studies. Silica gel is widely used in industry as a catalytic support and a greater understanding of reaction kinetics on these materials would be invaluable, particularly in regards to 20 optimising these applications.…”