Selective optical response to oxygen of membranes based on immobilized cobalt(II) porphyrins

New types of oxygen-sensitive membranes based on immobilized (meso-α,α,α,α-tetrakis(o-pivalamidophenyl)porphinato)cobalt(II) (CoP) were prepared, and their optical response behavior was studied. The complex CoP was immobilized on poly(octylmethacrylate-co-1-vinylimidazole) (OIm) and on poly(2,2,3,3,4,4,5,5-octafluoropentylmethacrylate-co-1-vinylimidazole) (OFIm), respectively. The selective recognition mechanism for an optical response to oxygen is based on the reversible formation of oxo-adducts at the cobalt(II) centers. The useful response range was found to cover 1-1000 hPa (mbar) of oxygen partial pressure, i.e., oxygen contents of 0.1-100% at atmospheric pressure. Optimum performance was achieved with the fluorinated CoP-OFIm membrane of 20 μm thickness, for which the 90% response time was 5-15 s, and the operational lifetime was longer than 1 month.