The protocovalent NO bond: Quantum chemical topology (QCT of ELF and ELI-D) study on the bonding in the nitrous acid HONO and its relevancy to the experiment

Topologically challenging, the protocovalent NO bond, which belongs to a distinct class called charge-shift bonds, has been identified in the HONO (cis, trans) molecules on the basis of topological analysis of the ELF and ELI-D functions obtained from the B3LYP and CASSCF(12,10) calculations. The presence of the protocovalent NO bond is associated with energetically possible dissociation channel: HONO(1A′) → OH(2π) + NO(2π).