Optical oxygen-sensing properties of porphyrin derivatives anchored on ordered porous aluminium oxide plates

An optical oxygen-sensing activity of anchored porphyrin derivatives on ordered porous aluminium oxide plates was studied in relevance to development of new oxygen-sensing systems. Porphyrin derivatives, 5,10,15,20-tetrakis(4-carboxylundecane-1-oxy) porphyrin ( 1(H)), 5-[4-(11-carboxyl-undecane-1-oxy)-10,15,20-triphenyl]porphyrin ( 2(H)), 5-(4-carboxylphenyl)-10,15,20-triphenylporphyrin ( 3(H)), and their platinum complexes, 5,10,15,20-tetrakis(4-carboxylundecane-1-oxy) porphyrinato-platinum( II) ( 1(Pt)), 5-[4-(11-carboxylundecane-1-oxy)-10,15,20-triphenyl] porphyrinato-platinum( II) ( 2(Pt)), 5-(4-carboxylphenyl)-10,15,20-triphenyl]porphyrinatoplatinum( II) ( 3(Pt)), were synthesized and anchored by an equilibrium adsorption method on aluminium oxide plates, which were prepared by an anodic oxidation. The excitation spectra of the porphyrin-anchored layers showed a broadened and blue-shifted Soret band compared with the corresponding porphyrins in DMSO. The luminescence intensity decreased with increasing oxygen concentrations. The oxygen-sensing ability estimated from I-0/I-100 ( I-0 and I-100 denote the luminescence intensity in 0 and 100% oxygen) was ( 1(H)) 9.08, ( 2(H)) 6.78, ( 3(H)) 8.71, ( 1(Pt)) 81.9, ( 2(Pt)) 35.5, and ( 3(Pt)) 39.1, which are greater than those of corresponding porphyrin derivatives in DMSO under the measured conditions, and indicates the remarkable enhancement effect of platinum( II). Non-linear Stern-Volmer plots were well. fitted by the two component system to give the oxygen-sensitive constant (KSV1/%(-1)), the oxygen-insensitive constant ( K-SV2/%(-1)), and the former contribution ( f(1)): ( 1(H)) 0.232, 3.32 x 10(-2), and 0.642; ( 2(H)) 0.141, 2.05 x 10(-2), and 0.687; ( 3(H)) 0.143, 1.05 x 10(-2), and 0.882; ( 1(Pt)) 17.3, 7.04 x 10(-3), and 0.980; ( 2(Pt)) 10.2, 1.43 x 10(-2), and 0.935; ( 3(Pt)) 16.3, 8.35 x 10(-3), and 0.954. The response time for the change of the atmospheric gas from argon to oxygen was ( 1(H)) 9.4 s, ( 2(H)) 12.5 s, ( 3(H)) 9.6 s, ( 1(Pt)) 5.0 s, ( 2(Pt)) 8.9 s, and ( 3(Pt)) 4.6 s, indicating the shortening effect of platinum. The reverse effect of platinum was observed in the change from oxygen to argon: ( 1(H)) 15.5 s, ( 2(H)) 17.0 s, ( 3(H)) 20.8 s, ( 1(Pt)) 667.4 s, ( 2(Pt)) 590.1 s, and ( 3(Pt)) 580.4 s, indicating the specific interaction of oxygen to the platinum( II) center.