Long-range N-N bonding by Rydberg electrons
By using high-level ab initio methods, we examine the nature of bonding between Rydberg electrons hosted by two four-coordinted nitrogen centers, embedded in a hydrocarbon scaffold. The electronic structure of these species resembles that of diradicals, yet the diffuse nature of the orbitals hosting the unpaired electrons results in unusual features. The unpaired Rydberg electrons exhibit long-range bonding interactions, resulting in stabilization of the singlet state (relative to the triplet) and a reduced number of effectively unpaired electrons. However, thermochemical gains due to through-space bonding are offset by strong Coulomb repulsion between positively charged nitrogen cores. The kinetic stability of these Rydberg diradicals may be controlled by judicious choices of molecular scaffold, suggesting possible strategies for their experimental characterization.