A 3D plot of molecular electrostatic potential (MEP) is used as a
visual method to analyze reactivity and relative polarity of atomic
sites of molecules including biomolecules and drugs. The MEPs of
(2E)-IPHC were computed at HF and B3LYP levels (Fig. 5) based on
their optimized geometrical positions. The MEPs were computed to
be between 0.06951 e and 0.06951 e in B3LYP and from 0.06166
e to 0.06166 e at the HF level.
The value of charges of MEP ranges from red (more negative) to
blue (more positive). The negative ion sites were observed near an
oxygen atom (O1) in the semicarbazide moiety and nitrogen atoms
in the imidazole ring. Due to the electron withdrawing effect of O1,
the nearby nitrogen atoms (N5 and N6) showed less negative potential.
On the other hand, the positive ion sites were observed
around the phenyl ring and methylene groups. The negative charge
of the carbon atoms in the phenyl ring was diminished due to the
effect of the other atoms attached to the phenyl ring. The magnitude
of MEP of all hydrogen atoms was positive. Both positive and
negative maxima were observed in the amide group, where the
maximum positive value was located at H34 and the maximum
negative potential was shown at N6.