New bis-di-organotin compounds derived from aminoacid-imine-hexadentate ligands. Multifunctional evaluation as corrosion inhibitors, antibacterials and asphaltene dispersants/inhibitors

A new class of bis-di-organotin (IV) compounds were synthesized in good yields (ca. 80%) by a one-step five molecules reaction in which intervene two molecular equivalents of leucine, one of 5,50-methylenebis-salicylaldehyde and either two of di-n-butyltin (IV) or diphenyltin (IV) oxides, that independently provided two bis-di-organotin derivatives. The structures of these two compounds were established by H, C and Sn NMR, as well as by IR and elemental analysis. In both cases the Sn chemical shifts are characteristic of pentacoordinated atoms in solution of non-coordinating solvent (CDCl3). Once characterized, the novel compounds were tested as corrosion inhibitors at 25, 50 and 100 mg L 1 on mild steel surfaces in sour brine by linear polarization resistance and potentiodynamic curves. These experiments prove that these derivatives present top efficiencies of 54% and 68% for butyl and phenyl moieties, respectively. In addition, these two compounds were tested in vitro against Bacillus subtilis (Gram-positive, strain ATCC 6633), Escherichia coli (Gram-negative, strain DH5) and Pseudomonas fluorescens strains to assess their bactericidal activities, being more effective for the E. coli strain, at concentrations as low as 25 mg L . Moreover, in order to correlate different activities and ascertain homologous action mechanisms, the two derivatives were tested for their asphaltene inhibition/dispersion activity. The results suggest that the presence of the four n-butyl moieties provide the needed amphiphillic balance to obtain better efficiencies in the tested activities. 2012 Elsevier Ltd. All rights reserved.