Ffrancon Williams

Bio: Ffrancon Williams is an academic researcher from University of Tennessee. The author has contributed to research in topics: Radical ion & Electron paramagnetic resonance. The author has an hindex of 28, co-authored 191 publications receiving 2527 citations. Previous affiliations of Ffrancon Williams include John Simon Guggenheim Memorial Foundation & Scuola Normale Superiore di Pisa.

Tunneling model for hydrogen abstraction reactions in low-temperature solids. Application to reactions in alcohol glasses and acetonitrile crystals

Abstract: A simple and internally consistent quantitative model for hydrogen-abstraction reactions in low-temperature solids, which implicitly incorporates zero point energy effects which allow for finite reaction rates at T = 0 K, is derived and applied to new measurements of H-abstraction rate constants by methyl radicals in methanol and ethanol glasses a t T = 13-99 K and in acetonitrile and methyl isocyanide crystals a t 69-128 K. Nonlinear least-squares fits of the model to the experimental data yield effective one-dimensional barriers to reaction whose heights are virtually independent of the analytic form used for the potential energy barrier, and are somewhat larger than the activation energies measured for the corresponding reactions in the gas phase. This model predicts that values of the isotopic rate constant ratio k H / k D will be larger than I O 1 * at T = 0 K. Quantum-mechanical tunneling has long been believed to make a dominant contribution to the rates of many chemical reactions at low temperatures.5,6 However, it is only relatively recently that convincing experimental evidence of this behavior has begun to appear. In most ~ t u d i e s , ~ ' ~ the evidence that the reactions considered proceeded mainly by tunneling consisted of (1) pronounced curvature in Arrhenius plots, (2) anomalously small activation energies, and (3) anomalously large10,'4 0002-7863/80/1502-2325$01.00/0

Structural Changes Accompanying Intramolecular Electron Transfer: Focus on Twisted Intramolecular Charge-Transfer States and Structures

Abstract: 6. Rehybridization of the Acceptor (RICT) 3908 7. Planarization of the Molecule (PICT) 3909 III. Fluorescence Spectroscopy 3909 A. Solvent Effects and the Model Compounds 3909 1. Solvent Effects on the Spectra 3909 2. Steric Effects and Model Compounds 3911 3. Bandwidths 3913 4. Isoemissive Points 3914 B. Dipole Moments 3915 C. Radiative Rates and Transition Moments 3916 1. Quantum Yields and Radiationless Deactivation Processes 3916

Proton-Coupled Electron Transfer

Abstract: ▪ Abstract Proton-coupled electron transfer (PCET) is an important mechanism for charge transfer in a wide variety of systems including biology- and materials-oriented venues. We review several are...

Organic mixed-valence compounds: a playground for electrons and holes.

Abstract: Mixed-valence (MV) compounds are excellent model systems for the investigation of basic electron-transfer (ET) or charge-transfer (CT) phenomena. These issues are important in complex biophysical processes such as photosynthesis as well as in artificial electronic devices that are based on organic conjugated materials. Organic MV compounds are effective hole-transporting materials in organic light emitting diodes (OLEDs), solar cells, and photochromic windows. However, the importance of organic mixed-valence chemistry should not be seen in terms of the direct applicability of these species but the wealth of knowledge about ET phenomena that has been gained through their study. The great variety of organic redox centers and spacer moieties that may be combined in MV systems as well as the ongoing refinement of ET theories and methods of investigation prompted enormous interest in organic MV compounds in the last decades and show the huge potential of this class of compounds. The goal of this Review is to give an overview of the last decade in organic mixed valence chemistry and to elucidate its impact on modern functional materials chemistry.

Perspective on Fluorocarbon Chemistry

Abstract: Fluorocarbons, organic molecules with carbon skeletons and fluorine "skins", differ fundamentally from their hydrocarbon counterparts in interesting and useful ways. A selection of the myriad applications fluorocarbons and their derivatives have found in modern life is described and related to molecular properties. Salient aspects of the nature and reactivity of fluorocarbon compounds are highlighted by comparison with their more familiar hydrocarbon analogues.