Quantum Molecular Parameters for the Prediction of Corrosion Inhibition potentials of some Alkaloids in Cryptocarya nigra Stem

Abstract

Babatunde T. Ogunyemi1* and Richard A. Ukpe

In recent times, the corrosion industry is intensively concentrated on the deployment of ecofriendly inhibitors to replace existing ones that are relatively toxic. In this study, a quantum chemical investigation into the suitability of some natural products in the bark extract of cryptocarya nigra was studied. Molecular reactivity descriptors of six alkaloids reportedly found in the bark of Cryptocarya nigra were probed to elucidate their electronic structures and match their expected reactivity and predict potential toward corrosion inhibition using the quantum mechanical method. The result obtained from DFT/B3LYP/6-31G(d) calculations indicated that three of the constituent alkaloids (Nmethylisococlaurine, methyllaurotetanine and 2-hydroxyathersperminine) displayed a strong tendency towards corrosion inhibition with theoretical data matching reported experimental values in literature. However, noratherosperminine was shown to be better at inhibiting iron corrosion than the other five due to their low energy gap, higher EHOMO, lower ELUMO and ΔN values which would allow effective electron transfer and therefore
better efficiency as a corrosion inhibitor. The relationship between the studied quantum parameters and reported experimental
inhibition efficiency of the studied molecules is useful in predicting Cryptocarya nigra alkaloids inhibitors with suitable substituents capable of donating electrons to the surface of the metal