3.2.2 MDA reaction on 6-6 double bond of
Li+@C60:
The preliminary adduct complex,
A16-6SL (7.7kcal/mol) is identified as
equally stable like its direct counterpart. As depicted inFigure 5 , the activation barrier corresponding to the
conversion of A16-6SL to
R16-6SL via
TS16-6SL is lowered by 4.2 kcal/mol
compared to its neutral counterpart. The associated enthalpy change
(-32.1kcal/mol) indicates that the second functionalization on
Li+-encapsulated fullerene via alternative way is also
thermodynamically feasible. In the third DA reaction, the barrier height
(TS16-6SL) corresponding to
R26-6Lformation is 14.1 kcal/mol,
which is almost comparable to its ‘Direct’ analogue. The exothermic
nature of the third DA reaction is also noted from the associated
enthalpy change (-27.3kcal/mol). Similar to the neutral
C60 analogue, for
Li+@C60 also, the addition of fourth
butadiene molecule will be obtained in a similar way to that of the
‘Direct’ one. Like the neutral C60 fabrication, for
Li+@C60also, all three DA steps are
synchronous as the maximum difference of bond length between the two C-C
bonds forming between the diene moiety and fullerene surface in the TS
is 0.026 Å.