Highly Oxidizing Excited States of Re and Tc Complexes
University of Wyoming, Ларами, Wyoming, United StatesJournal of the American Chemical Society (Impact Factor: 12.11). 01/2007; 128(51):16494-5. DOI: 10.1021/ja067114g
Like the Re analogue, the ligand-to-metal charge transfer (LMCT) excited-state of [Tc(dmpe)3]2+ (dmpe is bis-1,2-(dimethylphosphino)ethane) is luminescent in solution at room temperature. Surprisingly, both [M(dmpe)3]2+* species have extremely large excited-state potentials (ESPs) as oxidants-the highest for any simple coordination complex of a transition metal. Furthermore, this potential is available using a photon of visible light (calculated for M = Re(Tc); E1/2* = +2.61(2.52) V versus SCE; lambdamax = 526(585) nm). Using a Rehm-Weller analysis with a series of aromatic hydrocarbons as electron-transfer quenchers, E1/2(Re2+*/Re+) has been determined to be 2.58 V, in good agreement with the calculated value. Both [M(dmpe)3]2+* species are quenched by chloride ion and both can function as excited-state oxidants in water solution.
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ABSTRACT: This review describes recent advances in the photochemistry of complexes of the element rhenium. It covers not only fundamental chemistry but the recent applications of these complexes to supramolecular chemistry, carbon dioxide reduction, bioinorganic chemistry, sensors, and light-emitting devices.
Conference Paper: Spectroelectrochemical Sensor: Development and Applications[Show abstract] [Hide abstract]
ABSTRACT: This paper is being submitted to the 215th ECS (Electrochemical Society) Meeting, San Francisco, California | May 24-29, 2009 The spectroelectrochemical sensor concept uses electrochemistry to modulate an optical signal to give improved selectivity. The sensor consists of an optically transparent electrode/waveguide coated with a thin film that preconcentrates the analyte. The sensor concept was first demonstrated with ferricyanide and later it was shown to work on a complex sample by detecting ferrocycanide in radioactive Hanford tank waste. Nafion, partially sulfonated polystyrene-block-polyethylene-ran-butylene)block-polystyrene (SSEBS), and quaternized poly(vinylpyridine) (QPVP) are examples of polymers used for the thin film. Detection limits achieved by the sensor are 10-5 to 10-8 M using change in absorbance as the mode of detection and about 10-10 M using fluorescence. A sensor has been developed for detection of [Re(dmpe)3]+ where dmpe = dimethylphosphinoethane, which serves as a nonradioactive analogue for complexes of radioactive 99Tc. Some polycyclic aromatic hydrocarbons have appropriate electrochemical and spectroscopic properties for spectroelectrochemical detection as demonstrated for 1-hydroxypyrene and its conjugate 1-hydroxypyrene-glucuronide.
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ABSTRACT: A spectroelectrochemical sensor was developed for [Re(dmpe)3]+ as a nonradioactive analog for [Tc(dmpe)3]+. The sensor consists of an optically transparent electrode (OTE) coated with a thin film of sulfonated polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SSEBS). Colorless [Re(dmpe)3]+ was reversibly oxidized to [Re(dmpe)3]2+ (λmax=530 nm). [Re(dmpe)3]+ preconcentrated by ion-exchange into the SSEBS film, resulting in a 20-fold increase in peak current compared to a bare OTE after 1 h of exposure to aqueous [Re(dmpe)3]+ solution. Detection of [Re(dmpe)3]+ at concentrations down to 2×10−6 M was accomplished by electrochemical modulation of the complex and monitoring absorbance by attenuated total reflectance (ATR).
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