Polypyridylpropyne-Pd and -Pt porphyrin coating for visualization of oxygen pressure

Poly[1-trimethylsilyl-1-propyne-co-1-(3-pyridyl)propyne] 1 was prepared both as a polymer-ligand of a palladium porphyrin (PdOEP) and of a platinum porphyrin (PtTFP) and as a highly gaspermeable polymer matrix of the porphyrin. The porphyrin acted as a phosphorescence probe which could be quenched with oxygen and sense the oxygen partial pressure. 1 gave a smooth and tough coating with a thickness of ca. 2 μm which homogeneously involved the porphyrin. The porphyrin-1 coatings displayed strong red-colored phosphorescences (the emission maximum at 670 and 650 nm for PdOEP and PtTFP, respectively), and their intensity significantly decreased with an increase in the oxygen partial pressure on the coating. The high oxygen-quenching efficiency or the high oxygen pressure sensitivity of the porphyrin's phosphorescence was observed even at cryogenic temperature. Aggregation of the porphyrin was suppressed in the coating by ligation of the porphyrin with the nitrogenous residue of 1 to significantly reduce spatial noise in the phosphorescence measurement or the oxygen-pressure sensing. PtTFP-1 was coated on the surface of a delta wing model. The oxygen-pressure distribution on the coated model was successfully visualized in a cryogenic wind tunnel test.