meso-Tetraarylporpholactones as high pH sensorsElectronic supplementary information (ESI) available: Details of the alternative preparations of TFPL and TFPLPt, 13C, 1H, and 19F NMR spectra, IR spectra, etc. of these and comparison compounds in the absence and presence of base, UV-vis spectra of TFPL in different solvents and the presence of different bases, UV-vis TFPL acid titrations, etc. See DOI: 10.1039/c0an00018cPart 3 of the series Oxazolochlorins. Part 2: J. Akhigbe, C. Ryppa, M. Zeller

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. meso -Tetra(pentafluorophenyl)porpholactone and its Pt( ii ) complex respond to strongly alkaline conditions (pH 11.5 to 13.2) with a dramatic shift of their UV-vis spectra.