The ability of meso-tetra(pentafluorophenyl)porpholactone (T(F)PL) and its Pt(II) complex [meso-tetra(pentafluorophenyl)porpholactonato]Pt(II) (T(F)PLPt) to function as optical high pH sensors is described. Under strongly alkaline or high methoxide conditions, their UV-vis spectra undergo dramatic and reversible red-shifts. The dynamic range for the sensor T(F)PLPt in solution is from pH 11.5 to 13.2. Using (1)H, (19)F, and (13)C NMR, UV-vis and IR spectroscopy, mass spectrometry, and the use of model compounds, the molecular origin of this optical shift is deduced to be a nucleophilic attack of OH(-)/MeO(-) on the lactone carbonyl of the chromophore, representing a novel mechanism for porphyrin-based sensors. The sensing compound was solubilized with Cremophor EL for use in aqueous solutions and embedded in polymer matrixes for testing as optical fiber-based optodes and planar sheet optode materials.

Porpholactones are porphyrinoids in which one or more β,β′-bonds of the parent chromophore were replaced by lactone moieties. Accessible to varying degrees by direct and nonselective oxidations of porphyrins, the rational syntheses of all five dilactone isomers along stepwise, controlled, and high-yielding routes via porphyrin → tetrahydroxyisobacteriochlorin metal complexes → isobacteriochlorindilactone metal complexes or porphyrin → tetrahydroxybacteriochlorin → bacteriochlorindilactone (and related) pathways, respectively, are described. A major benefit of these complementary routes over established methods is the simplicity of the isolation of the dilactones because of the reduced number of side products formed. In an alternative approach we report the direct and selective conversion of free base meso-tetrakis­(pentafluorophenyl)­porphyrin to all isomers of free base isobacteriodilactones using the oxidant cetyltrimethylN+MnO4 –. The solid-state structures of some of the isomers and their precursors are reported, providing data on the conformational modulation induced by the derivatizations. We also rationalize computationally their differing thermodynamic stability and electronic properties. In making new efficient routes toward these dilactone isomers available, we enable the further study of this diverse class of porphyrinoids.

The reaction of singlet oxygen with water to form hydrogen peroxide was catalyzed by antibodies and has been termed as the antibody catalyzed water oxidation pathway (ACWOP) (Nieva and Wentworth, Trends Biochem. Sci. 2004, 29, 274-278; Nieva et al. Immunol. Lett. 2006, 103, 33-38). While conserved and buried tryptophans in the antibody are thought to play a major role in this pathway, our studies with a monoclonal antibody, mAb-1 and its mutant W53A, clearly demonstrate the role of surface-exposed tryptophans in production of hydrogen peroxide, via the photo-oxidation pathway. Reactive oxygen species (ROS) such as singlet oxygen and superoxide were detected and site-specific tryptophan (Trp53) oxidation was observed under these conditions using RP-HPLC and mass spectrometry. The single mutant of the surface exposed Trp53 to Ala53 (W53A) results in a 50% reduction in hydrogen peroxide generated under these conditions, indicating that surface exposed tryptophans are highly efficient in transferring light energy to oxygen and contribute significantly to ROS generation. ACWOP potentially leads to the chemical instability of mAb-1 via the generation of ROS and is important to consider during clinical and pharmaceutical development of mAbs.