A combined study on structures and vibrational spectra of the antiviral rimantadine using SQMFF and DFT calculations

IRAMAIN, MAXIMILIANO A.; HIDALGO, JOSÉ RUIZ; SUNDIUS, TOM; BRANDÁN, SILVIA ANTONIA

Heliyon

Elsevier

Año: 2022 vol. 8

2405-8440

In this research, a combined study on structures and vibrational spectra of antiviral rimantadine have beenperformed using hybrid B3LYP/6–311þþG** calculations and the scaled quantum force field (SQMFF) procedure.Harmonic force fields and scaled force constants of Free Base (FB), Cationic (CA) and Hydrochloride (HCl)species derived from the antiviral rimantadine have been calculated in gas phase and in aqueous solution usingnormal internal coordinates and scaling factors. Good correlations were acquired comparing the theoretical IR,Raman, 1H–13C-NMR and UV spectra of three species with the analogous experimental ones, suggesting probably,the presence of all them in both phases. The main force constants of three species have evidenced lower valuesthan the corresponding to antiviral amantadine. The ionic character of N1–H33⋯Cl36 bond of HCl species inaqueous solution evidence positive Mulliken charge on N1 atom indicating that this species is as CA one.Rimantadine presents higher solvation energies in water than other antiviral species, such as chloroquin, niclosamide,cidofovir and brincidofovir. The FB and HCl species of rimantadine are slightly less reactive than thecorresponding to amantadine while the opposite is observed for the CA species. The predicted ECD spectra for theFB and CA species show positive Cotton effect different from the negative observed for the HCl one. Thesedifferent behaviours of three species of rimantadine could probably explain the differences observed in the intensitiesof bands predicted in the electronic spectra of these species