Computational Studies of the Corrosion Inhibition Potentials of Quercetin and Coumarin

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Computational Studies of the Corrosion Inhibition Potentials of Quercetin and Coumarin

Journal Title: Archives of Organic and Inorganic Chemical Sciences - Year 2018, Vol 2, Issue 2

Abstract

The molecules of Coumarin and Quercetin were subjected to computational calculations using the Density Functional Theory (DFT) in order investigate their inhibition potentials. The Coumarin molecule demonstrated a greater corrosion inhibition potentials compared to the Quercetin molecule. The corrosion potentials were predicted using quantum chemical parameters like Energy of the highest occupied molecular orbital (EHOMO) and Energy of the lowest unoccupied molecular orbital (ELUMO), ionization potential (I), Fukui (f+ and f-) indices and Global hardness. The Computational study was carried out to calculate the electronic parameters for the Coumarin and Quercetin molecules. The following quantum chemical indices were considered to research the relationship of molecular structure and inhibition effect: the energy of the highest occupied molecular orbital (EHOMO), the energy of the lowest unoccupied molecular orbital (ELUMO), energy band gap AE = EHOMO - ELUMO, the electro negativity (x), global hardness (n), global electrophilicity («), global softness (a), and the change in the number of electrons transferred (AN), electron affinity, ionization potential, molecular weight, total dipole moment, Van der Waal's surface area. According to frontier molecular orbital theory, the chemical reactivity is a function of interaction between HOMO and LUMO levels of reacting species [1]. Theoretical calculations were conducted in order to provide molecular-level understanding of the corrosion inhibition behavior of Coumarin and Quercetin inhibitor. (Figures 1a & 1b) show the optimized structures, and (Figures 2a & 2b) show the HOMO and LUMO orbitals diagrams of Coumarin and Quercetin molecules respectively. The above listed parameters were considered to be of great importance in studying the chemical interaction between the inhibitors and the metal surface. Quantum chemical calculation is one of the widely used tools in corrosion studies [2]. In this work, different quantum chemical parameters were calculated and the results obtained from the DFT calculations were presented in Table 1. The most significant parameters in the semi empirical result are the frontier molecular energies, which are the energy of the highest occupied molecular orbital (EHOMO), the energy of the lowest unoccupied molecular orbital (ElumO) and the band energy gap (AE). The EHOMO correlates with the electron donating capacity of the specie. A higher value of EhomO is thus associated with better inhibitor [3]. On the other hand ElumO is connected with the affinity of the specie to accept electron [4]. Thus, the lower value of ElumO implies better efficiency. The energy gap of a molecule AE is related with the hardness and softness of the specie [5]. Larger energy gap implies that the molecule will need much energy to move from HOMO to the LUMO. Therefore, larger energy gap shows that the molecule is hard, while lower energy gap points toward soft molecule [6]. From the results presented in (Table 1), it is shown that quercetin is likely to be a better inhibitor than coumarin. This is because the EhOmO value of coumarin is relatively higher than that of quercetin. Similarly the ElumO value of coumarin is higher than quercetin and AE value of coumarin is higher than that of quercetin.

Authors and Affiliations

VM Udowo

Keywords

Lupine Publishers Lupine Publishers Group lupine publishers indexing Journals lupine publishers indexing list lupine publishers indexing sites Indexed Journals indexed journals list List of Indexed Journals lupine publishers impact factor lupine publishers open access journals lupine publishers indexing Lupine group Lupine online open access open access journals open access journals publishers lupinepublishers chemistry VM Udowo Quercetin inhibitor Quercetin molecule quantum chemical parameters ionization potential Quantum chemical Adsorption

EP ID EP602965
DOI 10.32474/AOICS.2018.02.000133
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