Phosphorus-nitrogen compounds Part 32. Structural and thermal characterizations, antimicrobial and cytotoxic activities, and in vitro DNA binding of the phosphazenium salts

The salicylic acid salts of fully substituted mono(4-fluorobenzyl)spirocyclotriphosphazenes (10-15) were prepared. The structures of these phosphazenium salts (10a-15a) were determined by elemental analyses, FTIR and H-1, C-13{H-1}, P-31{H-1} NMR techniques. The crystal structure of 14a was verified by X-ray diffraction analysis. The thermal properties of the salts were investigated using TG/DTA and DSC instruments. The results obtained from DSC indicated that the melting temperatures and latent heats of the compounds were in the ranges of 107.76-143.04 A degrees C and 41.64-69.73 J g(-1), respectively. The thermal stabilities of the phosphazenium salts (10a-15a) are found to be different, but they have a similar decomposition mechanism. The compounds 14a and 15a exhibit noticeable cytotoxic activity against DLD-1 cancer cells, and they seem to be good candidates for being anticancer agents. All of the compounds have an antimicrobial effect on bacterial and yeast strains within the ranges of 312-625 A mu M (bacterial strains) and 19.5-312 A mu M (yeast strains). It is found that compounds 13a-15a were most effective against yeast strains. Moreover, interactions between the salts and pBR322 plasmid DNA show that 14a and 15a cleave the DNA and decrease the intensity of form I. BamHI and HindIII digestion results demonstrate that the compounds are not bound with G/G and A/A nucleotides, respectively.