Arylphthalimidoporphyrins: New Approaches to Imaging pH and Temperature Simultaneously with Oxygen

Abstract

Tetraarylphalimidoporphyrins (TAPIP) and diarylphalimidoporphyrins (DAPIP) possess unique photophysical properties that enable new and superior approaches to optical biological sensing of pH and temperature in parallel with oxygen. The syntheses of TAPIP and DAPIP have been reported by our group recently. We also have reported the photophysical properties of free-base (H2), Zn(II), Pt(II) and Pd(II) DAPIP and TAPIP, including their non-linear spectroscopic properties, such as two- and three-photon absorption spectra. Using a combination of phosphorescent Pt complexes of TAPIP and DAPIP we are designing a phosphorescent sensor for pH and oxygen, termed pHOx, which operates by measuring ratios of phosphorescence lifetimes. Unlike all existing optical pH sensors, measurements by pHOx are not affected by optical heterogeneities of the medium and provide unbiased pH readings in vivo simultaneously with pO2. At the same time, Pd complexes of TAPIP have been shown to emit both phosphorescence and thermally activated E-type delayed fluorescence, providing a functional element for optical sensing of temperature. However, to make the temperature readings unobstructed by optical heterogeneities of biological tissue, a PdTAPIP-based probe is supplemented by another probe system, based on H2DAPIP, which emits prompt fluorescence at the same wavelengths and can serve as a correction standard for unbiased temperature measurements.