A comparison of experimental determinations of electron affinities of pi charge transfer complex acceptors
TL;DR: The absolute electron affinities of pi charge transfer complex acceptors have been examined and the "best" values have been chosen as discussed by the authors, and the magnetron results for anthraquinone and benzoquinone are not in agreement with the half-wave reduction potential data.
Abstract: The absolute electron affinities of pi charge transfer complex acceptors have been examined and the ’’best’’ values have been chosen. All of the results obtained by the magnetron method, including the estimates for hexafluorobenzene and tetracyanoethylene, were accepted. However, the magnetron results for anthraquinone and benzoquinone are not in agreement with charge transfer complex and half‐wave reduction potential data. The half‐wave reduction potential data and the charge transfer complex data for all of the other acceptors for which absolute electron affinities are available were found to be consistent with the usual correlation equations and their associated assumptions. The parameters from these correlations have been used to calculate the absolute electron affinities for about 150 acceptors.
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TL;DR: This work is concerned with the tunnelling of heavy particles: nuclei, atoms, molecules, which have wavelengths as large or larger than atoms at energies found in the valence shells of molecules.
Abstract: ‘Tunnelling’ is the metaphorical name given to the process, possible in quantum mechanics, but not in classical mechanics, whereby a particle can disappear from one side of a potential-energy barrier and appear on the other side without having enough kinetic energy to mount the barrier. One can think of this as a manifestation of the wave-nature of particles. The wavelength is larger if a particle is lighter. In particular electrons, being very light compared to atoms, have wavelengths as large or larger than atoms at energies found in the valence shells of molecules. Thus, they easily ooze through and around atoms and molecules. We are also concerned with the tunnelling of heavy particles: nuclei, atoms, molecules.
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TL;DR: In this article, the structural and electronic properties of polynitrile ligands are discussed, including their propensity to undergo π/π stacking, their non-innocent nature, and their ability to bridge several metal centers.
Abstract: Conjugated polynitriles such as TCNE or TCNQ can act as non-chelating polydentate ligands towards metal centres. Among the outstanding features of these ligands are (a) their propensity to undergo π/π stacking, (b) their non-innocent nature, i.e. their facile interconversion between three oxidation states, including a spin-bearing radical form, (c) their σ/π coordination ambivalence towards metals, and (d) their ability to bridge several metal centres, thus giving rise to oligonuclear complexes and coordination polymers. This article contains a survey of the structural and electronic features of metal complexes with TCNE, TCNQ and some related molecules. Guidelines are given to elucidate the type of coordination using vibrational data and to assign reasonable oxidation states to the redox-active polynitrile ligand; close-lying ligand π * MOS and d orbitals of coordinated transition metals can cause considerable orbital mixing. Attempts are made to relate coordination modes with electronic structures. Electron transfer dominates the chemical reactivity of the polynitriles and of their complexes, various consequences of initial electron transfer such as isomerization, polynucleation or substitutional rate enhancement are discussed. Interesting physical properties resulting from the extended π conjugation in metal complexes of the polynitrile ligands are briefly referred to by example of electrical conductivity, magnetic coupling and long-wavelength optical absorption.
281 citations
TL;DR: In this article, a method to arrange a TTF-TCNQ-based complex by the difference between the electrochemical half-wave potentials of the donor and acceptor molecules is proposed to predict electrical properties of the complex.
Abstract: Current theories on the origin of high electrical conductivity in TCNQ-based materials emphasize the need for incomplete charge transfer as well as segregated stacks of donor and acceptor molecules and uniform spacing within the stacks. The requirements for an “organic metal” are discussed in terms of partial charge transfer. An examination of 61 structurally related TTF–TCNQ, based complexes suggests that the combinations with the redox potential −0.02≤E1(D)−E1(A)≤0.34 V have a high possibility of being “organic metals.” A method to arrange the complex by the difference between the electrochemical half-wave potentials of the donor and the acceptor molecule is proposed to predict electrical properties of the complex.
170 citations
TL;DR: In this article, the authors found that electron tunneling reactions between trapped electrons and 48 organic electron acceptors in rigid 2-methyltetrahydrofuran glass at 77 K were observed from 10−6 to 102 s and measured tunneling distances were 15-40 A in most cases the o
Abstract: Many highly exothermic (2–3 eV) electron transfer reactions are shown to be slower than moderately exothermic reactions by factors as large as 105 The decrease occurs in a regular way with increasing exothermicity, tending to confirm theoretical predictions of Franck–Condon restrictions on strongly exothermic electron transfer reactions Deviations from the above trends occur if the reaction product, a molecular anion, has a low‐lying electronic excited state into which the reaction may occur with more moderate vibrational exothermicity Then greatly enhanced rates are found The rates are enhanced to a lesser extent for acceptors likely to undergo configurational changes upon accepting an electron These effects are found in measurements of rates of electron tunneling reactions between trapped electrons and 48 organic electron acceptors in rigid 2‐methyltetrahydrofuran glass at 77 K Electron tunneling rates were observed from 10−6 to 102 s Measured tunneling distances were 15–40 A In most cases the o
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TL;DR: In this article, the discovery of extraordinary conductivity maxima in a class of organic charge transfer salts is interpreted as resulting from superconducting fluctuations at high temperatures, and a possible mechanism for achieving high temperature superconductivity is suggested based on the electron-phonon interaction, in the strong coupling limit, and the Peierls soft-mode instability in pseudo-one-dimensional systems.
Abstract: The discovery of extraordinary conductivity maxima in a class of organic charge transfer salts is reported. The data are interpreted as resulting from superconducting fluctuations at high temperatures. A possible mechanism for achieving high temperature superconductivity is suggested based on the electron-phonon interaction, in the strong-coupling limit, and the Peierls soft-mode instability in pseudo-one-dimensional systems. Procedures are suggested for the possible eventual stabilization of the superconducting state.
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772 citations
TL;DR: In this article, the ionization potentials of eithtynine molecules have been determined by photoionization measurements and the results are tabulated and compared with those obtained by spectroscopic and electron impact methods.
Abstract: The ionization potentials of eithty‐nine molecules have been determined by photoionization measurements. The results are tabulated and compared with those obtained by spectroscopic and electron impact methods. Uncertainties in interpretation and several discrepancies are discussed.
540 citations