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 .