QUANTUM-CHEMICAL ANALYSIS OF THE ELECTRONIC STRUCTURES OF INHIBITING COMPLEXES OF RHAMNOLIPID WITH METALS

摘要

We perform the numerical analyses of the geometric and electronic structures of rhamnolipid (obtained as a product of biosynthesis of the Pseudomonas sp. PS-17 bacterial strain) based on the quantum-chemical density functional theory (DFT). We obtain the quantum-chemical parameters of the complexes of rhamnolipid with metals (calcium, zinc, aluminum, and copper), including the total energy of complexes, their heat of formation, the energies of the highest occupied molecular orbital and the lowest unoccupied molecular orbital, the value of the energy gap, ionization potential, distribution of atomic charges according to the Mulliken scheme, and some other derived characteristics. The results of quantum-chemical analyses also demonstrate that complex compounds of rhamnolipid can be formed as a result of its interaction with difficultly soluble calcium phosphate and zinc phosphate with simultaneous release PO43- of anions into the solution. It is shown that rhamnolipid molecules may enhance the anticorrosion effect as a result of facilitation of the electrolytic dissociation of difficultly soluble calcium phosphate and zinc phosphate and the increase in the concentration of phosphate ions in the medium. Moreover, we reveal the possibility of formation of stable rhamnolipid complexes with aluminum ions, which can precipitate on the surface of the metal in the form of a barrier organic layer that prevents their corrosion dissolution.