Judith R. Fish

Determination of nickel accumulation in single biological cells using porphyrinic microsensors

Carbon fiber ultramicroelectrodes modified with a conductive polymeric film of tetrakis(3-methoxy-4-hydroxyphenyl)nickel porphyrin (< 1–3 μm diameter) were used for monitoring the concentration of unbound nickel in individual BC3H-1 myocytes and H4-11-C3 rat hepatoma cells. Detection limits of 8×10−6 M and 1×10−6 M, respectively, were obtained. A method is described for fabricating sensors with the length and area of the electroactive surface appropriate for the dimensions of the cells under investigation. The method consists in carefully burning a fiber coated with wax in a controlled temperature gradient obtained with a microburner to sharpen the tip. The length and shape of the electroactive area obtained are controlled by the thickness of the wax coating, which is determined by the temperature of the melted wax. The sharpened tip of the 0.5–1-μm fiber was covered electrochemically with 10–90 monolayers of polymeric porphyrin, demetalated, implanted and used for nickel(II) accumulations and current determinations.

Electrochemistry and spectroelectrochemistry of a linear triiron cluster

Abstract This work reports electrochemical and spectroelectrochemical studies of a unique linear triiron cluster carbonyl complex, Fe 3 (CO) 7 L 2 , where L is a α-diazothioketone. Oxidation and reduction reactions have been observed in non-aqueous media over the temperature range −40 to 20 °C by differential pulse voltammetry, cyclic voltammetry, thin-layer, UV-Vis spectroelectrochemistry and ESR spectrometry. The sequence of the individual electron-transfer steps comprising the overall redox process is described, and a comparison between the electrochemistry of different non-linear iron carbonyl complexes is discussed. A single one electron reduction produces the radical anion, [Fe 3 (CO) 7 L 2 ]-, which decomposes at temperatures greater than −10 °C to species which are reduced at a more negative potential, an ECE mechanism. A single one-electron oxidation produces the radical cation, [Fe 3 (CO) 7 L 2 ] + , which is unstable, decomposing completely at room temperature, an EC mechanism. Spectroscopic evidence indicates that in non-bonding solvents, the Fe 3 (CO) 7 L 2 framework remains intact at low temperatures for both the anion and cation radical produced electrochemically with radical stability higher than might be expected for a linear structure. Observations indicate only strongly bonding solvents disrupt the structure. Low temperature stability occurs at relatively high temperatures, with the cation radical less than stable and vulnerable to strongly bonding solvents.

Spectroelectrochemical studies of cobalt(II) porphyrins with paracyclophanyl, pyridinium and nucleoside substituents

Abstract This work describes the synthesis of novel cobalt complexes of porphyrins: ( meso -tetrakis [2.2]paracyclophanylporphyrinato)cobalt(II) (T(PCP)PCo(II)); ( meso -mono[2.2]paracyclophanyltriphenylporphyrinato)cobalt(II) (PCPPCo(II)); ( meso -tetrakis(5′-0- p -phenylene-2′,3′-0-isopropylideneuridine)porphyrinato)cobalt(II) (TPUPCo(II)), and ( meso -5′-0- p -phenylene-2′,3′-0-isopropylideneuridinetri( N -methyl-4-pyridinium)porphyrinato)cobalt(II) (PUPCo(II)). The redox properties of these complexes were characterized by voltammetry and UV—visible spectroelectrochemistry. The effects of the electron-donating and electron-withdrawing properties of the substituents on the electrochemical and spectroscopic data obtained are described and discussed. These compounds are the first examples of a linkage of a biomolecule, such as uridine, with the porphyrin system. These porphyrins also undergo electrochemical polymerization with the formation of conductive films.

Conductive Polymeric Porphyrins - Characterization And Application For Amperometric Sensors

Highly conductive films have been obtained by oxidative polymerization of tetrakis (p-diethylaminop henyl ) porphyrins (p-Et2N)TPP and tetrakis(3-methoxy-4-hydroxyphenyl) porphyrins (TMHPP) with Fe, Pd, Cu, Ru, Ni, CO as central metals. These films were characterized by using vol tammet ry , ac impedance , UV-vi s i bl e spectroscopy, electron microscopy and x-ray photoelectron spectroscopy. Polymeric CuTMHPP produces a significant photosensitizati on effect and polymeric NiTMHPP can be efficiently demetallated and used as a microsensor for detection of nickel in single biological cells.