Computational studies of the corrosion inhibition potentials of some derivatives of 1H-Imidazo [4, 5-F] [1, 10] phenanthroline

Abstract

Computational simulations of the corrosion inhibition potentials of four imidazophenanthroline derivatives were carried
out using Density Functional Theory (DFT) with B3LYP/6-31G* method. It was shown that the predictive corrosion
inhibition potentials increase in the order 2-methyl-1H-imidazo[4,5-f][1,10]phenanthroline (MIP) < 3-(1H-imidazo [4, 5-f][1,
10] phenanthrolin-2-yl) phenol (IPP) <2-(2-methoxyphenyl)-1H-imidazo [4, 5-f] [1, 10] phenanthroline (MPIP) < 4-methoxy-
2-(3H-phenanthro [9, 10-d] imidazol-2-yl) phenol (MPP). The anticorrosion potentials were predicted using the quantum
chemical parameters like energy gap (?E), energy of highest occupied molecular orbital (EHOMO), energy of lowest unoccupied
molecular orbital (ELUMO), ionization potential (I), electron affinity (A), polarizability (?), global hardness (?), global softness
(), electronegativity (x) and polar surface area (PSA). Corrosion inhibition potentials increase with increasing EHOMO,
polarizability, global softness and polar surface area (PSA), and decreasing energy gap (?E), ELUMO and global hardness.
Also, the sites of likely electrophilic attack were located on nitrogen and oxygen atoms as shown by high negative
Mulliken charges of these atoms. This implied that the metal surface atoms could be bonded to these inhibitors through
nitrogen and oxygen atoms. From the results, 4-methoxy-2-(3H-phenanthro [9, 10-d] imidazol-2-yl) phenol (MPP) showed
the highest EHOMO, polarizability, PSA, and the lowest ?E, ELUMO, hence the greatest potential of inhibiting corrosion of
metals in aqueous solutions.