Bonding Analysis of the Shortest Bond between Two Atoms Heavier than Hydrogen and Helium: O₂²⁺

Abstract

Quantum chemical calculations using ab initio methods at the CCSD(T) level with large basis sets and DFT calculations using the BP86 functional have been carried out for O 2 2+ and N 2 . An energy decomposition analysis of the chemical bonds suggests that the shorter bond in O 2 2+ compared with isoelectronic N 2 is due to the weaker Pauli repulsion in the dication, which overcompensates the weakening of attractive interactions that are operative in N 2 . At the equilibrium distance of N 2 , the orbital (covalent) bonding in O 2 2+ is weaker than in N 2 , and the attractive Coulomb interactions in the neutral diatomic system become repulsive in the dication, but the weakening of the Pauli repulsion caused by the shrinking of the orbitals in O 2 2+ compensates for these forces and leads to a shortening of the bond. The results also show that the bond dissociation energy is not a reliable indicator for the strength of bond, which is more faithfully given by the (local) force constant.

The Existence of a N→C Dative Bond in the C60–Piperidine Complex

“…In conclusion, the short intermolecular distance and large stabilization energy indicate the formation of a new chemical entity with the dative bond between N (pip) and C (C 20 ). Several types of dative bonds have been reported previously [29, 33–41] …”

Highs and Lows of Bond Lengths: Is There Any Limit?

“…This is defined by the calculated hard sphere and spinodal points that occur at similar values in r e reduced units (0.766 and 1.28, respectively). Since the O 2 2+ cation displays the shortest bond length among molecules not containing H or He, [68] it is a good example to verify if it can be accounted for by our model. The stability limits of the neutral O 2 molecule (calculated form the RKR data showed in the SI as a reference) is used to construct the diagram of distances depicted in Figure 4 .…”

Highs and Lows of Bond Lengths: Is There Any Limit?

“…As it can be seen in this Figure,using the estimated intrinsic bond dissociation energy as ar eduction parameter,t he O 2 2+ curve overlaps quite well with those corresponding to prototypical molecules as O 2 ,F 2 O 2 and H 2 O 2 ,a tl east in the meaningful distance range of OÀO stability.T his is defined by the calculated hard sphere and spinodal points that occur at similar values in r e reduced units (0.766 and 1.28, respectively). Since the O 2 2+ cation displays the shortest bond length among molecules not containing H or He, [68] it is agood example to verify if it can be accounted for by our model. Thes tability limits of the neutral O 2 molecule (calculated form the RKR data showed in the SI as ar eference) is used to construct the diagram of distances Tabelle 1: Mechanical (r hs , r sp )a nd electronicr upture (r NNM , r BET ) distances for the CÀCbonds of the molecules summarized in Scheme 1.…”