4. Conclusion:
In this article, the MDA reaction on neutral C60 has
been computationally explored employing DFT where 6-6 as well as 6-5
bonds are considered. In addition, we have also investigated the effect
of Li+ encapsulation on the energetics of each step of
the MDA reaction. The consecutive attachments of butadiene molecules on
neutral C60 and
Li+@C60 commences with the formation
of a 1:1 precursor complex between the mono-functionalized fullerene
product and a butadiene molecule. In this regard, two possible
approaches (’Direct’ and ’Alternative’) have been considered separately,
leading to the same tri-functionalized fullerene product after two
consecutive additions of butadiene molecules. We have explored the MDA
reaction considering the attachment of a total of four diene molecules
on the surface of the fullerene cage. Each reaction step shows a high
degree of exothermicity, suggesting that the entire reaction is
thermodynamically feasible. However, from the PES diagrams, it is
evident that Li+ encapsulation makes a positive impact
by decreasing the activation barrier and increasing the reaction
enthalpy than their neutral counterparts. Thus, we can conclude that MDA
reactions become thermodynamically more facile due to
Li+ confinement in the C60 cage.
Moreover, in the MDA procedure also, the persistence of bond
selectivity, i.e., the higher reactivity of [6, 6] bonds over [6,
5], just like mono and bis-functionalization, has been noticed for
both C60 and Li+@C60.
In a nutshell, the exploration of all possible steps related to MDA
reaction on neutral as well as Li+ endohedral
C60 will motivate the researchers to investigate more
complex reactions related to fullerene chemistry for varied
applications.