Self-assembled synthesis, characterization and antimicrobial activity of zinc(II) salicylaldimine complexes

One-pot metal promoted reactions between salicylaldehyde and 4-methyl-1,3-phenylenediamine in the presence of metal salts acting as template agents yield zinc(II) salicylaldimine complexes containing N,N'-bis(salicylidene)-4-methyl-1,3-phenylenediamine (H2L) as a result of the [2 + 1] Schiff base condensation. The complexes of formula [Zn(HL)Cl(H2O)(2)]center dot C2H5OH and [Zn(H2L)(2)Cl(NO3)(H2O)]center dot CH3OH were characterized as powder solids and in solution by spectroscopic methods (IR, H-1 and C-13 NMR, FAB-MS, ESI-MS, UV-Vis), thermogravimetric and elemental analysis, potentiometry, and tested for antimicrobial activity against Staphylococcus aureus in a minimum inhibitory concentration (MIC) experiment. In these two powder solid species, the salicylaldimine, formed in a self-assembly process, acts in two different coordination modes: as monodeprotonated bidentate chelator with an N,O donor set or as a neutral monodentate using exclusively oxygen as the donor atom without involving the nitrogen atoms in the coordination. However, crystals of these two complexes are isomorphous, with 1:2 metal: ligand stoichiometry, and display the latter, relatively rare coordination pattern. In solution, the presence of a 1:1 complex of monodeprotonated state is only detected. The complexes exhibit antimicrobial activity against S. aureus. (C) 2009 Elsevier B. V. All rights reserved.