Odd‐Electron Bonds

Abstract

The history and theory of one‐ and three‐electron bonds are presented and discussed. It is shown that the dependence of the odd‐electron bond energy on the difference in ionization potentials of the bonding partners must be corrected to include the ion‐pairing energy for neutral odd‐electron bonded complexes.

Trapping One Electron between Three Beryllium Atoms: Very Strong One‐Electron Three‐Center Bonds

“…Fullerenes also yield very stable anions, acting as electron traps, through the formation of one‐electron intermolecular C−C σ‐bonds and multicenter two‐electron bonds to give trimers analogous to H 3 + , whereas the high E ea of the radical anionic 1,8‐X,X′‐naphtalene boron‐containing derivatives is also related to the formation of B‐B one‐electron bonds . A very interesting review on odd‐electron bonds has been recently published by Clark …”

“…[19] Av ery interesting review on odd-electron bonds has been recently published by Clark. [20] In this context, we would like to highlight the role played by the scaffold that maintains the BeX groups close together.I n this field, like in supramolecular chemistry,n ot only the geom-The ability of as et of beryllium-substitutedc yclohexane derivatives to trap electrons wasd etermined by evaluating their electron affinities at the G4(MP2) level of theory.T he nature of bondinga nd the effect of the different substituents attached to berylliumw ere studied by different computationalm ethods (quantumt heory of atoms in molecules, electron localization function, natural bond orbital, and analysisoft he spin density), revealing the existence of ao ne-electron/Be 3 cyclic bondingi n trisubstituted species. This peculiar bond is the key for the high electron affinity values found in the tri-BeX derivatives (X = F, Cl, CN), such as the triberyllium cyano derivatives of cyclohexane, reachingv alues of 294 kJ mol À1 ,o nly marginally smaller than the valuesr eported for tetracyanoethylene (305 kJ mol À1 )a nd for somefullerenes (306 kJ mol À1 ).…”

Aromatic Charge Resonance Interaction Probed by Infrared Spectroscopy

“…[1] Radical ions of arenes are involved in chemical reaction mechanisms, charge transport of modern (bio-)organic materials (organic electronics), and radiation damage in DNAand proteins. This description of the CR interaction in arene dimer ions is similar to the one employed for odd electron chemical bonds in radical ions (hemibonds) [5] and exciton splitting in delocalized electronic excitation in neutral dimers. [4] Forc ations,t his stabilization arises from sharing the positive charge between two identical or different molecules with the same or comparable ionization energies in a p-stacked dimer.I nahomodimer cation (A 2 + ), the positive charge is equally shared between both molecules, while in ah eterodimer (AB + )t he partner with the lower ionization energy (IE) carries more positive charge.I nt he simplest description, the CR interaction in A 2 + causes as plitting between the two electronic states described by Y AE = Y(A + )Y(A) AE Y(A)Y(A + ); the symmetric Y + ground state is stable and the destabilized antisymmetric Y À state is repulsive.The splitting between both electronic states is twice the stabilization energy of the ground state (ca.…”

“…[2] In addition to p H-bonding,c ation/anion-p,a nd p-p stacking interactions, [3] the charge-resonance (CR) interaction is af undamental and very strong force in charged arene dimers. This description of the CR interaction in arene dimer ions is similar to the one employed for odd electron chemical bonds in radical ions (hemibonds) [5] and exciton splitting in delocalized electronic excitation in neutral dimers. 50-100 kJ mol À1 ).…”

“…This description of the CR interaction in arene dimer ions is similar to the one employed for odd electron chemical bonds in radical ions (hemibonds) [5] and exciton splitting in delocalized electronic excitation in neutral dimers. 50-100 kJ mol À1 ).…”