Structural characterization and biological evaluation of polynuclear Mn(II) and Cd(II) complexes with 2,2-dimethyl-1,3-propanediamine-N,N,N’,N’-tetraacetate. The influence of ligand structure and counter cation on the complex nuclearity

Abstract

© 2020 Elsevier Ltd New polynuclear manganese(II) and cadmium(II) complexes with 2,2-dimethyl-1,3-propanediamine-N,N,N’,N’-tetraacetato ligand (2,2-diMe-1,3-pdta), {Ba[M(2,2-diMe-1,3-pdta)].3H2O}n (M = Mn (1) or Cd (2)) were synthesized and characterized by IR spectroscopy and single-crystal X-ray diffraction analysis. In addition, complex 2 was characterized by solution 1H and 13C NMR spectroscopy. Crystallographic analysis showed that 2,2-diMe-1,3-pdta ligand is hexadentately coordinated to each M(II) ion through the two nitrogen and four carboxylate oxygen atoms, whereas the one of these oxygen atoms is also involved in coordination to the second M(II) ion of the dinuclear [M2(2,2-diMe-1,3-pdta)2]4− unit in polymeric structures. Moreover, three of four carboxylic groups of 2,2-diMe-1,3-pdta ligand are additionally bonded to four Ba(II) ions, in three distinctive bridging coordination modes. Each Ba(II) ion is surrounded by ten oxygen atoms, seven belonging to carboxylate groups of 2,2-diMe-1,3-pdta, and three belonging to water molecules. The coordination environment around Mn(II) and Cd(II) ions could be assigned as a face capped octahedron, while coordination polyhedron around Ba(II) ion in these two complexes was described as a distorted sphenocorona. The antimicrobial potential of complexes 1 and 2 and corresponding metal salts used for their synthesis was evaluated against different bacterial and Candida spp. Both complexes showed selective antifungal activity against the tested Candida spp. compared to the bacterial strains, with the minimal inhibitory concentration (MIC) values in the range 3.12 – 12.50 µM. Moreover, complex 1 caused the slightly decrease of hyphae length, while no significant influence on hyphal length of complex 2 was observed. With aim to assess the therapeutic profile of the complexes, their cytotoxicity was evaluated against the normal human lung fibroblast cell line (MRC-5).