Molecular dynamics simulations and quantum chemical calculations for the adsorption of some imidazoline derivatives on iron surface

K.J Uwakwe,A.I Obike,A.I Ikeuba,P.C Okafor

doi:10.4314/gjpas.v23i1.8

Abstract

The molecular dynamic (MD) simulation and quantum chemical calculations for the adsorption of [2-(2-Henicos-10-enyl-4,5-dihydro-imidazol-1-yl)-ethyl]-methylamine (HDM) and 2-(2-Henicos-10-enyl-4,5-dihydro-imidazol-1-yl)-ethanol (HDE) on iron surface was studied using Materials Studio software. Molecular dynamic simulation results indicate that the imidazoline derivative molecules uses the imidazoline ring to effectively adsorb on the surface of iron, with the alkyl hydrophobic tail forming an n shape (canopy like covering) at geometry optimization and at 353 K. The n shape canopy like covering to a large extent may prevent water from coming in close contact with the Fe surface. The quantum chemical calculation based on the natural atomic charge, the frontier molecular orbital and the Fukui indices values and plots shows the active sites of the molecules to be mainly the N=C-N region in the imidazoline ring, others include the nitrogen and oxygen heteroatoms in the pendant part and the double bonded carbon atoms in the hydrophobic tail of the imidazoline derivative molecules. The quantum chemical calculations also reveal that the amine group in HDM and the hydroxyl group in HDE which is attached to the imidazoline ring do not result in a significant increase in the HOMO nor the LUMO density which can aid adsorption.HDM has a lower energy gap of 4.434 eV and 3.824 eV, a higher E HOMO of -4.273 eV and -4.152 eV and a higher global softness of 0.45 and 0.52 compared to HDE which have an energy gap of 4.476 eV and 4.084 eV, a E HOMO of -4.349 eV and -4.607 eV and a global softness of 0.45 and 0.49 at geometry optimization and at 353 K. The adsorption ability of the molecule is given as at geometry optimization HDM > HDE and at 353 K HDM > HDE. Theoretically HDM is a better inhibitor than HDE. The adsorption ability of the molecule is in line with the binding energy at the temperature studied.

Highlights

Amines and their salts are said to be the most economic and effective corrosion inhibitors for oil and gas wells (Schauhoft and Kissel, 1999)
Are shown in Figure 1 (a), (b), (c) and (d).Equilibration of the system was established by the steady average values of energy as well as temperature (Xia et al, 2008).The calculated interaction, binding energy and the distance between the inhibitor molecules and the iron surface obtained from molecular dynamics simulation are shown in
The molecular dynamic simulation results indicate that the imidazoline derivatives will most likely use the imidazoline ring to effectively adsorb on the surface of iron, with the alkyl hydrophobic tail forming an n shape at both at geometry optimization and at 353 K

Summary

INTRODUCTION

Amines and their salts are said to be the most economic and effective corrosion inhibitors for oil and gas wells (Schauhoft and Kissel, 1999). Their modes of adsorption on iron surface, their adsorption ability and the active sites of this molecules using Molecular dynamic simulation considering properties such as interaction/binding energy, bond length, natural atomic charge and quantum chemical parameters such as dipole moment ( ), energy of deformation (Đ),energy of the highest occupied molecular orbital (EHOMO), energy of the lowest unoccupied molecular orbital (ELUMO), energy gap (ΔE), total energy (E), electron affinity (A), ionization potential (I), global hardness (ƞ), global softness (S), and Fukui functions f(r) at the geometry optimized and at 353 K structures. Computational Details for Quantum Chemical Calculation Quantum chemistry calculations were done using two modules available in the Material studio 4.0 (from Accelrys Inc.) software These modules are Vamp (which is a highly efficient semi empirical molecular orbital package) and Dmol (which is a program which uses the density functional theory (DFT) with a numerical radial function basis set to calculate the electronic properties of molecule clusters, surfaces and crystalline solid materials from the first principle). The colour codes for the atoms in the molecules studied are gray for carbon, blue for nitrogen, red for oxygen and white for hydrogen

RESULTS AND DISCUSSION

Molecular dynamic simulation

CONCLUSIONS