# A Computational (DFT) Study on the Anti-Malarial Drug: Lumefantrine
## 3 Results and Discussion
### Electronic and Spectral Properties  
Electronic transitions and spectral properties were calculated in each method. HOMO and LUMO molecular orbital surfaces were calculated and depicted. Their energy values were also tabulated and compared to each other. An ESPMap (Electrostatic potential Map) is calculated and presented as figures (Figure 2). Figure 1: (**a**) Basic molecular structure and atom numbering of Lumefantrine, (**b**) molecular formula of artemether and (**c**) 4-aminoquinoline. An ESPMAP (Electrostatic Potential Map) is a visualization tool used to represent the electrostatic potential of a molecule. It provides valuable information about the distribution of positive and negative charges within the molecule, which can be helpful in understanding various aspects of its chemical properties. Here are some reasons why an ESPMAP is important:  
1. Molecular reactivity: The electrostatic potential is closely related to the reactivity of a molecule. It can provide insights into regions of high electron density (negative potential) that are likely to be involved in nucleophilic reactions, as well as regions of low electron density (positive potential) that are susceptible to electrophilic attacks. By examining the ESPMAP, chemists can predict sites of potential chemical reactions and understand the reactivity patterns of the molecule. 2. Intermolecular interactions: The electrostatic potential plays a crucial role in intermolecular interactions, such as hydrogen bonding, van der Waals forces and solvation effects. An ESPMAP can help identify regions of positive or negative potential that are involved in these interactions. For example, the negative potential regions can indicate favorable sites for hydrogen bonding while positive potential regions can attract negatively charged species or induce dipole-dipole interactions. 3. Molecular recognition: An ESPMAP is particularly useful in studying molecular recognition, such as ligand-protein interactions in drug design. By comparing the electrostatic potentials of a ligand and its target protein, researchers can identify complementary regions of positive and negative potentials that facilitate binding. Understanding the electrostatic complementarity between molecules aids in rational drug design and the development of more potent and selective compounds. 4. Solvent effects: Solvent molecules can influence the electrostatic potential of a molecule, leading to changes in its properties and reactivity. An ESPMAP can help visualize how solvent molecules affect the distribution of charges and identify regions where solvation effects are significant. This knowledge is crucial in understanding the behavior of molecules in solution and predicting their behavior under different solvent conditions. 5. Molecular properties: The electrostatic potential is closely related to various molecular properties, including molecular electrostatic potential (MEP), molecular dipole  
Figure 2: Calculated ESPMaps for Lumefantrine. moment and polarizability. An ESPMAP can provide insights into these properties, allowing researchers to analyze and compare different molecular features. Overall, an ESPMAP is an important tool for understanding the electronic structure, reactivity and interactions of molecules. It helps chemists and researchers gain a visual understanding of the charge distribution within a molecule, enabling them to make informed predictions and design experiments or simulations for a wide range of chemical applications [29]. Lumefantrine has 30 C atoms, 32 H atoms, 3 Cl, 1 O and 1 N atoms, 67 atoms in total. So it is better to handle the molecule in two graphics for Mulliken charge distribution. The first graphic shows the charge distribution of H atoms, and the second one depicts C and heteroatoms. Like every molecule, atoms of Lumefantrine have different electronegativities, so the electron distribution on the molecule is heterogeneous. More electronegative atoms attract and gather up more electrons than the electropositive ones.