Pushing the limits of the electrochemical window with pulse radiolysis in chloroform.

Pulse radiolysis (PR) enables the full redox window of a solvent to be accessed, as it does not require electrodes or electrolyte which limit the potentials accessible in voltammetry measurements. PR in chloroform has the additional possibility to enable reaching highly positive potentials because of its large ionization potential (IP). PR experiments demonstrated the formation of the (deuterated) chloroform radical cation CDCl3+˙, identifying it as the source of the broad absorption in the visible part of the spectrum. Results indicated that solutes with a redox potential up to +3.7 V vs. Fc/Fc+ can be oxidized by CDCl3+˙, which is far beyond what is possible with electrochemical techniques. Oxidation is not efficient because of rapid geminate recombination with chloride counterions, but also due to rapid decomposition of CDCl3+˙ which limits the yield of otherwise longer-lived free ions. The rapid, 6 ± 3 ns, decomposition, confirmed by two independent experiments, means that a solute must be present at a concentration >100 mM to capture >90% of the free holes formed. Addition of ethene removes the broad, overlapping absorptions from ubiquitous (chlorine atom, solute) complexes created by PR in halogenated solvents enabling clear observation of solute cations. The results also unravel the complex radiation chemistry of chloroform including the large reported value G(-CHCl3) = 12 molecules/100 eV for the decomposition of chloroform molecules.

[1]  Kelley J. Rountree,et al.  A Practical Beginner’s Guide to Cyclic Voltammetry , 2017 .

[2]  V. Borovkov.  Unexpectedly Large Spin Coherence Effects in the Recombination Fluorescence from Irradiated Highly Polar Solutions on a Nanosecond Time Scale. , 2017, The journal of physical chemistry. B.

[3]  G. M. Greetham,et al.  Photoisomerization and photoinduced reactions in liquid CCl4 and CHCl3. , 2013, The journal of physical chemistry. A.

[4]  John R. Miller,et al.  Rapid "step capture" of holes in chloroform during pulse radiolysis. , 2013, The journal of physical chemistry. A.

[5]  T. Kozawa,et al.  Geminate charge recombination in liquid alkane with concentrated CCl4: effects of CCl4 radical anion and narrowing of initial distribution of Cl-. , 2011, The journal of physical chemistry. A.

[6]  M.-J. Lu,et al.  Resonant dissociative electron transfer of the presolvated electron to CCl4 in liquid: Direct observation and lifetime of the CCl4*- transition state. , 2008, The Journal of chemical physics.

[7]  C. Cramer,et al.  Single-ion solvation free energies and the normal hydrogen electrode potential in methanol, acetonitrile, and dimethyl sulfoxide. , 2007, The journal of physical chemistry. B.

[8]  C. Cramer,et al.  Aqueous solvation free energies of ions and ion-water clusters based on an accurate value for the absolute aqueous solvation free energy of the proton. , 2006, The journal of physical chemistry. B.

[9]  J. K. Thomas,et al.  The Laser Two-photon Photolysis of Liquid Carbon Tetrachloride† , 2006, Photochemistry and photobiology.

[10]  R. Fujiyoshi,et al.  Reaction of CS2/Cl complexes with alcohols studied by pulse radiolysis , 2005 .

[11]  Andrew R. Cook,et al.  The LEAF picosecond pulse radiolysis facility at Brookhaven National Laboratory , 2004 .

[12]  U. Scherf,et al.  Hole formation and transfer in poly[9,9-di(ethylhexyl)fluorene] and an amine end-capped derivative in solution , 2004 .

[13]  Y. Katsumura,et al.  Geminate ion kinetics for hexa-, Penta- and tetrachloroethane in liquid methylcyclohexane (MCH): Effect of the anion lifetimes , 2003 .

[14]  K. Ohkubo,et al.  Driving force dependence of intermolecular electron-transfer reactions of fullerenes. , 2003, Chemistry.

[15]  L. E. Horsburgh,et al.  Pulse radiolysis studies on charge carriers in conjugated polymers , 2000 .

[16]  Y. Katsumura,et al.  CHLOROFORM ANION FRAGMENTATION IN LIQUID METHYLCYCLOHEXANE : T-0.6 SIMULATION OF THE GEMINATE ION KINETICS , 1999 .

[17]  A. C. Albrecht,et al.  MOBILITIES OF RADICAL CATIONS AND ANIONS, DIMER RADICAL ANIONS, AND RELATIVE ELECTRON AFFINITIES BY TIMES OF FLIGHT IN N-HEXANE , 1994 .

[18]  J. Chateauneuf.  Spectroscopic detection and reactivity of the chlorine atom-carbon disulfide molecular complex , 1993 .

[19]  I. Gould,et al.  Efficiencies of photoinduced electron-transfer reactions: role of the Marcus inverted region in return electron transfer within geminate radical-ion pairs , 1990 .

[20]  J. Chateauneuf.  Direct measurement of the absolute kinetics of chlorine atom in carbon tetrachloride , 1990 .

[21]  J. Chateauneuf.  Charge-transfer absorption spectra of chlorine atoms in halogenated solvents , 1989 .

[22]  E. A. Walters,et al.  Dissociation energies of the benzene dimer and dimer cation , 1987 .

[23]  H. Miyasaka,et al.  Picosecond 266 nm multiphoton laser photolysis of liquid alkyl chlorides: Production of ionic species , 1985 .

[24]  M. Hyder,et al.  Radiolysis of Chloroform in the Intense Radiation Pulse from a Nuclear Explosion , 1968, Nature.

[25]  R. F. Firestone,et al.  Kinetics of the γ-Ray-Induced Decomposition of Chloroform1 , 1965 .

[26]  G. A. Russell,et al.  Solvent Effects in the Reactions of Free Radicals and Atoms. VIII. The Photochlorination of Aralkyl Hydrocarbons , 1963 .

[27]  K. Wong,et al.  EFFECTS OF TEMPERATURE AND ADDED HEXACHLOROETHANE ON THE RADIOLYSES OF CARBON TETRACHLORIDE AND CHLOROFORM , 1961 .

[28]  M. Ottolenghi,et al.  The radiation chemistry of chloroform. , 1961, Radiation research.

[29]  T. H. Chen,et al.  RADIOLYSIS OF CHLOROFORM AND CARBON TETRACHLORIDE , 1960 .

[30]  A. Henglein,et al.  Die Zersetzung des Chloroforms durch Gamma-Strahlen und durch Ultraschallwellen , 1958 .

[31]  M. Washio,et al.  Pulse radiolysis of polystyrene and benzene in cyclohexane, chloroform and carbon tetrachloride , 1983 .

[32]  H. Burrows,et al.  SOLUTE RADICAL CATION YIELDS IN THE PULSE RADIOLYSIS OF SOLUTIONS OF AROMATIC AMINES IN CHLORINATED HYDROCARBONS. , 1972 .

[33]  N. Bibler.  DOSE RATE EFFECTS IN THE STEADY AND PULSE RADIOLYSIS OF LIQUID CHLOROFORM. , 1971 .

[34]  N. Bibler,et al.  Positive Ion Scavenging in the Radiolysis of Liquid Chloroform , 1970 .

[35]  R. F. Firestone,et al.  Pulse‐Radiolysis Observation of Molecular Cations of Aromatic Compounds in Halogenated Liquids , 1969 .

[36]  R. Bühler,et al.  Transient Charge-transfer Complexes with Chlorine Atoms by Pulse Radiolysis of Carbon Tetrachloride Solutions , 1967, Nature.

[37]  R. F. Firestone,et al.  COMBINED EFFECTS OF DOSE RATE AND TEMPERATURE IN THE RADIOLYSIS OF LIQUID CHLOROFORM. APPLICATION OF HOMOGENEOUS KINETICS TO THE RADIOLYTIC SYSTEM. , 1966 .