Synthesis and characterization of Cu(II) complexes of proton transfer salts derived from piperazine derivatives and 5-sulfosalicylic acid

In this study, proton transfer salts (H₂Etpip)(Hssa), (H₂HOEtpip)(Hssa) and (HAcpip)(H₂ssa), have been obtained by reactions between 1-ethylpiperazine (Etpip), 1-(2-hydroxyethyl)piperazine (HOEtpip) and 1-acetylpiperazine (Acpip) and 5-sulfosalicylic acid (H3ssa). Also, Cu(II) complexes of proton transfer salts (H₂Etpip)[Cu(Hssa)2]·5H₂O, (H₂HOEtpip)[Cu(Hssa)₂]·5H₂O and (H₂Acpip)[Cu(Hssa)₂]·5H₂O) have been synthesized. The structures of proton transfer salts have been proposed by using FT-IR, ¹H and ¹³C NMR spectroscopy, and elemental analysis. The structures of the amorphous metal complexes have been proposed by atomic absorption spectrometry, FT-IR, magnetic susceptibility, molar conductivity techniques, and elemental analysis. Antimicrobial activities of compounds have been tested against Staphylococcus aureus (ATCC 29213) (Gram-positive), Escherichia coli (ATCC 25922) (Gram-negative), Candida krusei (ATCC 6258) (yeast), and Candida parapsilosis (ATCC 22019) (yeast) microorganisms. For S. aureus, the minimum inhibitory concentration (MIC) values of the synthesized salts were between 31.25 and 62.50 µg/ml, and 15.60 µg/ml for complexes. The MIC values of salts and complexes for E. coli were in the range 125.00 - 500.00 µg/ml and 31.25 - 62.50 µg/ml, respectively. The MIC values of the salts for C. krusei were 62.50 µg/ml, and for the complexes in the range 15.60 - 31.25 µg/ml. For C. parapsilosis, these values were 31.25 µg/ml for all salts and in the range 15.60 - 62.50 µg/ml for complexes. (author)