Quantum-chemical study of the structure and vibrational spectrum of the PEG5 polyethylene glycol oligomer complex with the KCl ion pair

Quantum-chemical ab initio Hartree-Fock method using the 6-31G+(d) basis was used to calculate the spatial and electronic structure of the PEG5 polyethylene glycol oligomer complex consisting of five repeating units with the KCl ion pair. A comparative analysis of the structural and energy changes that occur during the formation of the PEG5+KCl complex with the previously studied PEG5 complexes with potassium, sodium, chlorine and ionic NaCl pairs were carried out. The investigated models of the complexes were obtained as a result of preliminary modeling on the basis of calculations carried out by the molecular dynamics method. The calculation of the energy and geometric parameters of the complexes was carried out. The main structural rearrangements and changes in the electronic structures at the formation of all studied The calculation confirmed that the stabilization of such complexes is ensured by the formation of coordinating interactions of potassium or sodium cations with oxygen atoms, and the chlorine anion with the terminal hydrogen of the polyethylene glycol chain. The theoretical vibrational spectra of the PEG5+KCl complex was studied by the ab initio Hartree-Fock method using 6-31G + basis. Theoretical interpretation of the obtained theoretical vibrational spectrum in the distribution of potential energy in vibrational coordinates was carried out using the VEDA-4 program.