Cyclodextrins improve the antimicrobial activity of the chloride salt of Ruthenium(II) chloro-phenanthroline-trithiacyclononane.

The complex [Ru([9]aneS(3))phenCl]Cl (phen = 1,10-phenanthroline) and its synthetic precursor [Ru([9]aneS(3))dmsoCl(2)] were immobilized in permethylated beta-cyclodextrin (TRIMEB). A new crystalline structure of the precursor, obtained from a batch ethanol solution at low temperature (4 degrees C), is fully described from single-crystal X-ray diffraction data. [Ru([9]aneS(3))phenCl]Cl was also encapsulated in native beta-cyclodextrin for comparison with the TRIMEB compound. All three compounds were obtained with a 1:1 host:guest stoichiometry and were studied by powder X-ray diffraction (including synchrotron radiation data), thermogravimetric analysis (TGA), (13)C{(1)H} CP/MAS NMR and FTIR spectroscopies. The bacterial growth inhibitory action of the complex [Ru([9]aneS(3))phenCl]Cl and its two cyclodextrin compounds was tested on Gram-negative (Salmonella, Escherichia) and Gram-positive strains (Bacillus, Listeria, Enterococcus and Staphilococcus) and results show a positive effect of cyclodextrin immobilization on the antimicrobial properties.