3.3. Charges, molecular electrostatic potential and bond orders
studies
Atomic charges, molecular electrostatic potentials and bond orders are
interesting properties that can easily explain the behaviour of S(-) and
R(+) enantiomers in different media, as it was reported for the two
enantiomeric forms of scopolamine alkaloid and antihistaminic
promethazine [76,77]. Those two species have also tertiary amine
groups as the two forms of CQ, hence, in scopolamine the N atom that
belongs to the N-CH3 group is linked to a ring while in
promethazine has a C-N-(CH3)2 group. But
in both species of chloroquine the amine tertiary groups are
C-N-(CH2-CH3)2·groups.
Hence, some differences are expected in these forms of CQ, as compared
with those two species. Here, two types of atomic charges for S(-) and
R(+) forms of CQ in both media, the Merz-Singh-Kollman (MK) and natural
population atomic (NPA) charges were studied by using B3LYP/6-311++G**
level of theory. In Table S1 those calculated charges on all
atoms of both enantiomeric forms of CQ can be seen. The behaviour of
both charges on the Cl1, N2, N3 and N4 atoms are particularly presented
in Figure 3 .