From charge transfer to electron transfer in halogen-bonded complexes of electrophilic bromocarbons with halide anions

2015 ◽  
Vol 17 (7) ◽  
pp. 4989-4999 ◽  
Author(s):  
Sergiy V. Rosokha ◽  
Alfredo Traversa
Keyword(s):  
Electron Transfer ◽  
Charge Transfer ◽  
Halogen Bonding ◽  
Dramatic Decrease ◽  
Halide Anions ◽  
Inner Sphere ◽  
Bonded Complexes

Halogen bonding leads to a dramatic decrease of the barrier for (inner-sphere) electron transfer and halogen transfer between bromocarbons and iodide anions.

Zur Theorie der Elektronenübergangsreaktionen in molekularen Komplexen / Theory of Electron Transfer Reactions in Molecular Complexes

1974 ◽  
Vol 29 (6) ◽  
pp. 880-887 ◽  
Author(s):  
P. P. Schmidt
Keyword(s):  
Activation Energy ◽  
Electron Transfer ◽  
Charge Transfer ◽  
Rate Constant ◽  
Reaction Rate ◽  
Charge Transfer Complex ◽  
Rate Theory ◽  
Transfer Step ◽  
Donor And Acceptor ◽  
Inner Sphere

This paper reports a theory of the inner sphere-type electron transfer reaction. Inner sphere reactions, as opposed to the outer sphere variety, require that the solvate or ligand shells surrounding the electron donor and acceptor species undergo considerable change in the course of the electron transfer. In this paper we assume that the electron transfer step takes place in a molecular complex which exists in equilibrium with the reactants. The electron transfer step occurs as a non-radiative charge transfer-type transition. In this manner we treat the charge transfer kinetics, in particular, the evaluation of the reaction rate constant, in the same manner as is usual for non-radiative problems. The analysis leading to the rate constant expression is based on Yamamoto’s general chemical reaction rate theory. The rate constant expressions obtained are quite general, they hold for any degree of strength of coupling between subsystems comprising the entire system. The activation energy, in the Arrhenius form for the rate constant, shows a dependence on the energy (work) of formation of the intermediate charge transfer complex, on vibrational shift energies associated with the molecular motions of the ligands, and on solvent repolarization energies. The activation energy also shows an important dependence on coupling terms which link the vibrations of the molecular inner shell with the polarization states of the (assumed) dielectric continuum which surrounds the charge transfer participants. The approach we take in developing this theory we believe points the way towards the development of a more complete theory capable of accounting for the dynamics of the molecular reorganization leading to the intermediate charge transfer complex as well as accounting for the electron transfer step itself.

Electron-transfer reactions of halogenated electrophiles: a different look into the nature of halogen bonding

2017 ◽  
Vol 203 ◽  
pp. 315-332 ◽  
Author(s):  
Sergiy V. Rosokha
Keyword(s):  
Electron Transfer ◽  
Charge Transfer ◽  
Halogen Bond ◽  
Structural Characteristics ◽  
Halogen Bonding ◽  
Outer Sphere ◽  
Ferrocene Derivatives ◽  
Dissociative Electron Transfer ◽  
Covalent Interaction ◽  
Electron Transfer Theory

The rates of oxidation of ferrocene derivatives by brominated molecules R-Br (CBr3CN, CBr4, CBr3NO2, CBr3COCBr3, CBr3CONH2, CBr3F, and CBr3H) were consistent with the predictions of the outer-sphere dissociative electron-transfer theory. The similar redox-reactions of the R-Br electrophiles with the typical halogen-bond acceptors tetramethyl-p-phenylenediamine (TMPD) or iodide were much faster than calculated using the same model. The fast redox-processes in these systems were related to the involvement of the transient halogen-bonded [R-Br, TMPD] or [R-Br, I−] complexes in which barriers for electron transfer were lowered by the strong electronic coupling of reactants. The Mulliken–Hush treatment of the spectral and structural characteristics of the [R-Br, TMPD] or [R-Br, I−] complexes corroborated the values of coupling elements, Hab, of 0.2–0.5 eV implied by the kinetic data. The Natural Bond Orbital analysis of these complexes indicated a noticeable donor/acceptor charge transfer, Δq, of 0.03–0.09 ē. The Hab and Δq values in the [R-Br, TMPD] and [R-Br, I−] complexes (which are similar to those in the traditional charge-transfer associates) indicate significant contribution of charge-transfer (weakly-covalent) interaction to halogen bonding. The decrease of the barrier for electron transfer between the halogen-bonded reactants demonstrated in the current work points out that halogen bonding should be taken into account in the mechanistic analysis of the reactions of halogenated species.

Optimized Electron Transfer in Charge-Transfer Ion Pairs. Pronounced Inner-Sphere Behavior of Olefin Donors

1996 ◽  
Vol 118 (16) ◽  
pp. 3842-3851 ◽  
Author(s):  
Stephan M. Hubig ◽  
T. Michael Bockman ◽  
Jay K. Kochi
Keyword(s):  
Electron Transfer ◽  
Charge Transfer ◽  
Ion Pairs ◽  
Inner Sphere
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