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This investigation was undertaken to determine whether the Fukui
functions, the local softnesses, or the local charges can predict the pre-
ferred donor sites of porphycenes toward metal ions.
In this work[14],we have adopted two very popular calculation proce-
dures[15-18] for the calculation of the global and local reactivity descrip-
tors of porphycene to fi nd whether the Fukui functions, the local softness-
es or the local charges can predict the preferred donor sites of porphycenes
toward metal ions.
This analysis was performed using fully optimized AM1 geometries
and the Hückel method. With the help of AM1 and Hückel molecular or-
bital (HMO) calculation procedures, we study the local reactivity param-
eters for better understanding of the preferred sites for coordination with
the metal ion (electron acceptor) of porphycene. We also venture to study
the global reactivity parameters for them for the better understanding of
the stability of porphycene. The semiempirical method is invoked to study
the charge distribution on the different atomic sites of porphycene and
hence to analyze the use of different reactivity descriptors for the predic-
tion of the coordination sites for them.
9.1.1 THE GLOBAL REACTIVITY PARAMETERS
9.1.1.1 IONIZATIONPOTENTIAL
The ionization energy, or ionization potential, is the energy required to
completely remove an electron from a gaseous atom or ion. The closer and
more tightly bound an electron is to the nucleus, the more difficult it will
be to remove, and the higher its ionization energy will be. The first ioniza-
tion energy is the energy required to remove one electron from the parent
atom. The second ionization energy is the energy required to remove a
second valence electron from the univalent ion to form the divalent ion,
and so on. Successive ionization energies increase. The second ionization
energy is always greater than the first ionization energy. Ionization ener-
gies increase moving from left to right across a period (decreasing atomic
radius). Ionization energy decreases moving down a group (increasing
atomic radius). Group I elements have low ionization energies because the
loss of an electron forms a stable octet.
 
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