Pressure Tuning of Electron Attachment to Benzoquinones in Nonpolar Fluids: Continuous Adjustment of Free Energy Changes

Inverted Region in Bimolecular Electron Transfer in Solution Enabled by Delocalization

Rate constants for bimolecular electron transfer (ET) increased with driving force, -ΔG°, reached a plateau, and then decreased in an inverted region. This rate data was described well by electron transfer theory subject to a diffusion-controlled limit. These were for ET from radical anions of polydecylthiophene (P3DT) to a series of acceptors in THF solution. When the donor was the smaller anion of quaterthiophene (T₄^•-) the inverted region was much less prominent and still less so for when the donor was the anion of bithiophene (T₂^•-). Description of the data using ET theory identifies smaller electronic couplings for the highly delocalized P3DT anions as enabling the inverted behavior: The presence of a Marcus inverted region is a consequence of delocalized electronic states. The results further imply that electronic couplings smaller than usually found for molecules in contact could boost efficiency of energy storage by electron transfer and identifies size-mismatch as an important concept in control of electronic couplings.

Electron transfer in nonpolar media

Electron transfer in nonpolar media violates the temperature scaling predicted by the fluctuation–dissipation theorem.

Electronic structure of the para-benzoquinone radical anion revisited

Photoinduced processes in para-benzoquinone anion are studied with multistate multireference perturbation theory: an interplay between autodetachment and internal conversion.

Energy of the quasi-free electron in H2, D2, and O2: Probing intermolecular potentials within the local Wigner-Seitz model

We present for the first time the quasi-free electron energy V0(ρ) for H2, D2, and O2 from gas to liquid densities, on noncritical isotherms and on a near critical isotherm in each fluid. These data illustrate the ability of field enhanced photoemission (FEP) to determine V0(ρ) accurately in strongly absorbing fluids (e.g., O2) and fluids with extremely low critical temperatures (e.g., H2 and D2). We also show that the isotropic local Wigner-Seitz model for V0(ρ)--when coupled with thermodynamic data for the fluid--can yield optimized parameters for intermolecular potentials, as well as zero kinetic energy electron scattering lengths.

First-Principles Calculations of the Energy and Width of the (2)A(u) Shape Resonance in p-Benzoquinone: A Gateway State for Electron Transfer

Quinones are versatile biological electron acceptors and mobile electron carriers in redox processes. We present the first ab initio calculations of the width of the (2)A(u) shape resonance in the para-benzoquinone anion, the simplest member of the quinone family. This resonance state located at 2.5 eV above the ground state of the anion is believed to be a gateway state for electron attachment in redox processes involving quinones. We employ the equation-of-motion coupled-cluster method for electron affinity augmented by a complex-absorbing potential (CAP-EOM-EA-CCSD) to calculate the resonance position and width. The calculated width, 0.013 eV, is in excellent agreement with the width of the resonant peak in the photodetachment spectrum, thus supporting the assignment of the band to resonance excitation to the autodetaching (2)A(u) state. The methodological aspects of CAP-EOM-EA-CCSD calculations of resonances positions and widths in medium-sized molecules, such as basis set and CAP box size effects, are also discussed.