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We report the large scale syntheses and 'oxidative purification' of fcI 2 , fcBr 2 and FcBr (fc = ferrocene-1,1'diyl, Fc = ferrocenyl). These valuable starting materials are typically laborious to separate via conventional techniques, but can be readily isolated by taking advantage of their increased E 1/2 relative to FcH/FcX contaminants. Our work extends this methodology towards a generic tool for the separation of redox active mixtures. Scheme 1 Synthesis and oxidative purification of (a) FcI (Goeltz and Kubiak), 21 and fcBr, and (b) fcI 2 and fcBr 2 (this work) (A − = Cl − , [FeCl 3 ] − or [FeCl 4 ] − ).

ABSTRACT:We report the synthesis and full characterization of the entire haloferrocene (FcX) and 1,1'-dihaloferrocene (fcX 2 ) series (X = I, Br, Cl, F; Fc = ferrocenyl, fc = ferrocene-1,1'-diyl). Finalization of this simple, yet intriguing set of compounds has been delayed by synthetic challenges associated with the incorporation of fluorine substituents. Successful preparation of fluoroferrocene (FcF) and 1,1'-difluoroferrocene (fcF 2 ) were ultimately achieved using reactions between the appropriate lithiated ferrocene species and N-fluorobenzenesulfonimide (NFSI). The crude reaction products, in addition to those resulting from analogous preparations of chloroferrocene (FcCl) and 1,1'-dichloroferrocene (fcCl 2 ), were utilized as model systems to probe the limits of a previously reported 'oxidative purification' methodology. From this investigation and careful solution voltammetry studies, we find that the fluorinated derivatives exhibit the lowest redox potentials of each of the FcX and fcX 2 series. This counter-intuitive result is discussed with reference to the spectroscopic, structural and first principles calculations of these and related materials.

pH homeostasis is strictly controlled at a subcellular level. A deregulation of the intra/extra/subcellular pH environment is associated with a number of diseases and as such, the monitoring of the pH state of cells and tissues is a valuable diagnostic tool. To date, only a few tools have been developed to measure the pH in living cells with the spatial resolution needed for intracellular imaging. Among the techniques available, only optical imaging offers enough resolution and biocompatibility to be proposed for subcellular pH monitoring. We present herein a ratiometric probe based on upconversion nanoparticles modified with a pH sensitive moiety for the quantitative imaging of pH at the subcellular level in living cells. This system provides the properties required for live cell quantitative imaging i.e. positive cellular uptake, biocompatibility, long wavelength excitation, sensitive response to pH within a biologically relevant range, and self-referenced signal.

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