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Synthesis, density functional theory study and in vitro antimicrobial evaluation of new benzimidazole Mannich bases

  • Marinescu, Maria1
  • Cinteză, Ludmila Otilia2
  • Marton, George Iuliu3
  • Chifiriuc, Mariana-Carmen4, 5
  • Popa, Marcela4, 5
  • Stănculescu, Ioana2
  • Zălaru, Christina-Marie1
  • Stavarache, Cristina-Elena6
  • 1 University of Bucharest, Bucharest, 050663, Romania , Bucharest (Romania)
  • 2 University of Bucharest, Bucharest, 030018, Romania , Bucharest (Romania)
  • 3 University “Politehnica” of Bucharest, 1-7 Polizu, Bucharest, 011061, Romania , Bucharest (Romania)
  • 4 University of Bucharest, 1-3 Aleea Portocalilor, Bucharest, 60101, Romania , Bucharest (Romania)
  • 5 Research Institute of the University of Bucharest, 91-95 Splaiul Independentei, Bucharest, 050095, Romania , Bucharest (Romania)
  • 6 Institute of Organic Chemistry “C.D. Nenitzescu” of the Romanian Academy, 202B Splaiul Independentei, Bucharest, 060023, Romania , Bucharest (Romania)
Published Article
BMC Chemistry
Springer International Publishing
Publication Date
Jul 25, 2020
DOI: 10.1186/s13065-020-00697-z
Springer Nature


The tri-component synthesis of novel chiral benzimidazole Mannich bases, by reaction between benzimidazole, aqueous 30% formaldehyde and an amine, the biological evaluation and DFT studies of the new compounds are reported here. The 1H-NMR, 13C-NMR, FTIR spectra and elemental analysis confirm the structures of the new compounds. All synthesized compounds were screened by qualitative and quantitative methods for their in vitro antibacterial activity against 4 bacterial strains. DFT studies were accomplished using GAMESS 2012 software and HOMO–LUMO analysis allowed the calculation of electronic and structural parameters of the chiral Mannich bases. The geometry of 1-methylpiperazine, the cumulated Mullikan atomic charges of the two heteroatoms and of the methyl, and the value of the global electrophilicity index (ω = 0.0527) of the M-1 molecule is correlated with its good antimicrobial activity. It was found that the presence of saturated heterocycles from the amine molecule, 1-methyl piperazine and morpholine, respectively, contributes to an increased biological activity, compared to aromatic amino analogs, diphenylamino-, 4-nitroamino- and 4-aminobenzoic acid. The planarity of the molecules, specific bond lengths and localization of HOMO–LUMO orbitals is responsible for the best biological activities of the compounds.

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