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rol. However, when we look at the pi charge density, ZDO, and Mulliken
charges on the atomic sites we surprisingly noted that they are maximum
on the N atom of the pyrrol and hence it is the donor site of the base.
9.4.2 PORPHYCENE
The analysis of the densities of HOMO (Figure 9.3(A)) shows that both
the orbitals are centered on the four C atoms of two adjacent pyrrol rings
only. The analysis of the densities of LUMO (Figure 9.3(B)) shows that
the distribution of electron cloud is of two types. In type-1 both the orbit-
als are centered on the two C atoms of two pyrrol rings, and in type orbit-
als are delocalized over the rings.
We have applied simple HMO theory for the computation of π charge
density on each atomic site of the porphycene. The computed results are
presented in Table 9.3(A). An observation on Table 9.4(A) reveals that
the π charge density on atom number C-1,C-10,C-11,C-20 and C-2,C-
9,C-12,C-19, and C-3,C-8,C-13,C-18,and C-4,C-7,C-14,C-17, and C-
5,C-6,C15,C-16 are the same and that on the four N -atoms is the same
and maximum. We can say that the decreasing order of the charge C-2,C-
9,C-12,C-19> C-3,C-8,C-13,C-18> C-4, C-7,C-14,C-17 > C-1,C-10,C-
11,C-20 > C-5,C-6,C-15,C-16 from this output which is in accord with
our normal experiences. We have also computed the bond orders and bond
lengths for porphyrin on the basis of HMO theory and presented in Tables
9.3(B) and (C), respectively
It is transpires from Table 9.7 that with respect to the f + and f values
the centers C-1,C-10,C-11,C-20; C-2,C-9,C-12,C-19; C-3,C-8,C-13,C-
18;C-4,C-7,C-14,C-17; C-5,C-6,C-15,C-16; N-21,N-22,N-23,N-24; are
identical. It can be also noted that the centers C-5,C-6,C-15,C-16 have
the highest f + value (0.16669538) and the centers C-2,C-9,C-12,C-19 have
the lowest f + value (0.02138312) and the centers N-21,N-22,N-23,N-24
have the highest f value (0.12280968) and the centers C-2,C-9,C-12,C-
19,C-3,C-8,C-13,C-18,C-5,C-6,C-15,C-16 have the lowest f value
(0.05030792).
It is distinct from Table 9.7 that the local softnesses of each atomic
sites of porphycene follow exactly the same trend of variation of Fukui
function.
The AM1 Fukui functions and local softnesses are presented in Table
9.9. Considering the f + ( r ) and f ( r ) value we can say from the Table 9.9
 
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