QUANTUM COMPUTATIONAL STUDIES ON PORPHYCENE - Theoretical and Computational Research in the 21st Century - page 191

that the N-1,N-4 centers, N-10,N-13 centers, C-2,C-3 centers, C-7,C-16
centers, C-5,C-14 centers C-6,C-15 centers, C-8,C-9, centers C-11,C-12
centers ,C-17,C-24 centers, C-20,C-21 centers, C-18,C-23 centers and the
C-19,C-22 centers are identical.
A observation on Table 9.9 reveals that the center C-7,C-16 have the
lowest and C-8,C-9 have the highest f + ( r ) value and the center C-7,C-16
has the lowest and C-5,C-14 has the highest f − ( r ) value.
It is distinct from Table 9.9 that the local softnesses of each atomic sites
of porphycene follow the similar trend of variation like Fukui function.
An observation on Table 9.11 reveals that on the basis of AM1 calcula-
tion, the two sets of N-centers have high atomic charge value. The N-1 and
N-4 have the maximum atomic charge and the other set N-10 and N-13
have also very high atomic charge. This observation supports the view that
two trans N atoms donate two lone pairs of electrons to metal ion during
donor acceptor interaction. The observation of the work is the Fukui func-
tion and local softness on the N atoms is not the maximum but the charges
on the N atoms are maximum in both ZDO and Mulliken method. The
same observations are also found in case of HMO calculation, where the
Fukui functions and local softness are not the maximum on the N atoms,
but on some C atom, which contradicts the experimental observations.
Thus, we may point out that the Fukui function fails to predict the donor
site of pyrrol and porphycene. But when we look on the pi charge density,
ZDO and Mulliken charges on the atomic sites we surprisingly noted that
they are maximum on the N atoms of the pyrrol and porphycene and hence
it is the donor site of the compounds under study.
9.5 CONCLUSION
A theoretical study of the stability, reactivity, and site selectivity was car-
ried out at the AM1 and Huckel method. Further we made an attempt to
compare the local reactivity indices of the DFT (Fukui function and local
softness) and atomic charges. This study provides evidence that both the
Fukui functions and local softnesses fail to explain the maximum reac-
tive or more precisely the donor site of the molecule/ligand porphycene.
However, the π charge density, ZDO, and Mulliken charges show maxima
on the Trans N atoms. We surprisingly noted that two sets of the trans N
atoms of the molecule has the same atomic charge and higher in magni-
tude than all C atoms.