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

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

▪ 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...

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Proton-Coupled Electron Transfer

Modern aspects of the Jahn-Teller effect theory and applications to molecular problems.

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.

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

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.

Perspective on Fluorocarbon Chemistry

The rate of polymerization of liquid isobutyl vinyl ether conforms to an Arrhenius temperature dependence with an overall activation energy of 6.6 kcal/ mole between --78 and 90 deg C. Also, it was found that the rate of polymerization at 30 deg C depends on the 0.65-power of the dose rate. Evidence was obtained that such results do not preclude an ionic mechanism. By studying the effect of added ion (proton) scavengers in very low concentration on the rate of polymerization, it was established that ions play the predomr-nant role as chain intermediates. The effectiveness of ammonia as a retarder for the polymerization indicates that the reaction is cationic. (P.C.H.)

Evidence for an ionic mechanism in the radiation-induced polymerization of isobutyl vinyl ether

Anisotropy of Nitrogen Hyperfine Coupling and g Factor in the ESR Spectra of Trapped Electrons in Gamma‐Irradiated Crystalline Organic Cyanides

Radiation-induced isomerization of 1-bromobutane by a free radical chain reaction

The radiation-induced polymerization of ..beta..-pinene carried out in bulk at ca.25/sup 0/ has been studied for different methods of monomer drying. It has been confirmed that the polymerization is sensitive to adventitious moisture and that substantial polymer yields (ca. 10% conversion per Mrad) can only be obtained under extremely dry conditions. Complete inhibition of the reaction by added tripropylamine corroborates the view that the polymerization is cationic. About half of the polymer formed is insoluble in the monomer. The number-average molecular weights for the soluble poly(..beta..-pinene) fraction have been measured by vapor pressure osmometry and are in the narrow range from 1700 to 2400 with little or no dependence on the degree of monomer conversion to polymer, at least up to 80%. The results are compared with literature reports on the polymerization of ..beta..-pinene by catalytic initiators.

Ffrancon Williams

Papers

Evidence for an ionic mechanism in the radiation-induced polymerization of isobutyl vinyl ether

Anisotropy of Nitrogen Hyperfine Coupling and g Factor in the ESR Spectra of Trapped Electrons in Gamma‐Irradiated Crystalline Organic Cyanides

Radiation-induced isomerization of 1-bromobutane by a free radical chain reaction

Radiation‐induced cationic polymerization of β‐pinene

Electron spin resonance spectrum of trifluoramine oxide(1-) ion. Hypervalent radical from first-row elements