Synthesis, spectroscopic, electrochemical, DFT and SAR studies of nifuroxazide complexes with Pd(II), Pt(II) and Ru(II)

[Ru(NIF)Cl2(OH2)2]·4H2O (1), and [M(NIF)Cl2]·zH2O (M(II) = Pd (2), z = 6; and Pt (3), z = 4) complexes (NIF = nifuroxazide) were synthesized, and characterized using elemental analysis, FT IR, 1H NMR, UV–Vis, TG/DTA, magnetic, and conductivity measurements. NIF coordinated to the metal ions as a neutral bidentate ligand via CO, and hydrazone N. The experimental studies were correlated with the quantum chemical calculations performed at DFT/B3LYP/LANL2DZ level of theory. The natural charge of the Ru(II) ion was more reduced than the Pd(II), and Pt(II) ions suggesting the higher complexation ability of NIF towards the former ion. NIF showed two reversible reduction peaks in DMF at E1/2 −0.75, and −1.26 V corresponding to the reduction of NO2 to NHOH. Coordination of NIF (0.072 μmol/mL) to a Pd(II) center 2 (0.029 μmol/mL) led to important increase in the antibacterial activity. Structural–activity relationship suggested that ELUMO, dipole moment and molecular electrostatic potential maps were the most significant descriptors for the correlation with the antibacterial activity.

Graphical abstractCoordination of nifuroxazide drug to Pd(II) ion led to important increase in its antibacterial activity. Toxicity can be related to charge sign and surface map value of the nitro group.Figure optionsDownload full-size imageDownload as PowerPoint slide