Noble gas encapsulated B₄₀cage

Abstract

The efficacy of B borospherene to act as a host for noble gas atoms is explored via density functional theory based computations. Although the Ng@B complexes are thermochemically unstable with respect to dissociation into free Ng and B, it does not rule out their viability as all the systems possess a high activation free energy barrier (84.7-206.3 kcal mol). Therefore, once they are formed, it is hard to take out the Ng atom. Two Ng atoms can also be incorporated within B for the lighter Ng atoms (He and Ne). In fact, the destabilization offered by the encapsulation of one and two He atoms and one Ne atom inside B is significantly less than that in experimentally synthesized He@CH, highlighting their greater possibility for synthesis. Although Ar and Kr encapsulated B systems are very much destabilized by the repulsive interaction between Ng and B, an inspection of the bonding situation reveals that the confinement can even induce some degree of covalent interaction between two otherwise non-bonded Ng atoms. Ng atoms transfer electrons towards B which is smaller for lighter Ng atoms and gradually increases along He to Rn. Even if the electrostatic interaction between Ng and B is the most predominant term in these systems, the extent of the orbital interaction is also considerable. However, the very large Pauli repulsion counterbalances the attractive interaction, eventually turning the interaction repulsive in nature. Ng@B also shows dynamical behaviour involving continuous exchange between hexagonal and heptagonal holes, similar to the host cage, as understood from the very little variation in the activation barrier because of the Ng encapsulation. Furthermore, sandwich complexes like [(η-CMe)Fe(η-B)] and [(η-CMe)Fe(η-B)] are noted to be viable with the latter being slightly more stable than the former. The encapsulation of Xe slightly improves the dissociation energy associated with the decomposition into Xe@B and [Fe(η-CMe)] compared to that in the bare one.

Noble gas endohedral fullerenes

“…The ab initio MD study on Ng 2 @C 60 showed that Ng 2 units, including He 2 , undergo translational, vibrational, and rotational movements as a single entity, without any random movement, supporting some sort of bonding between two He atoms. 57 A similar situation was noted in Ng 2 conned in a smaller cavity like B 12 N 12 , B 16 N 16 , and B 40 cages 106,107 where some specic descriptors support bonding and some criteria do not. Therefore, it is only a matter of weightage an individual wants to give.…”

How Far Can One Push the Noble Gases Towards Bonding?: A Personal Account

“…Borospherene (B 40 ) can also encapsulate Ng atoms and systems like Ng n @B 40 (n = 1 for He-Rn; n = 2 for He-Kr) [140] have been studied using DFT methods. The systems are not thermodynamically stable with respect to the dissociation to B 40 cage and free Ng atoms, but once the entrapped cages are formed, they are kinetically stable due to a high free energy barrier (Δ G ‡ ).…”

Confinement Effects of a Noble Gas Dimer Inside a Fullerene Cage: Can It Be Used as an Acceptor in a DSSC?

“…Cerpa et al ( 2009 ) have studied the effect of confinement on the electronic interaction between He-He bond in the host C 20 H 20 and their results followed that a shorter He-He bond does not always indicate a chemical bond. Not only are the carbon related compounds considered as the hosts for entrapping the Ng atoms and their dimers, but hosts constituted with other elements such as B 40 cage (Pan et al, 2018 ), B 12 N 12 (Khatua et al, 2014a ; Paul et al, 2019 ), B 16 N 16 (Khatua et al, 2014a ), , and (Sekhar et al, 2017 ) are also reported. Encapsulation of Ng and Ng 2 in B 12 N 12 and B 16 N 16 fullerenes show that the dimer He 2 undergoes not only vibration and translation, but also rotation inside the cage.…”