The FT-IR spectra of pyrazinamide complexes of transition metal(II) tetracyanonickelate

A Nanostructured Lipid System as a Strategy to Improve the in Vitro Antibacterial Activity of Copper(II) Complexes

The aim of this study was to construct a nanostructured lipid system as a strategy to improve the in vitro antibacterial activity of copper(II) complexes. New compounds with the general formulae [CuX₂(INH)₂]·nH₂O (X = Cl⁻ and n = 1 (1); X = NCS⁻ and n = 5 (2); X = NCO⁻ and n = 4 (3); INH = isoniazid, a drug widely used to treat tuberculosis) derived from the reaction between the copper(II) chloride and isoniazid in the presence or absence of pseudohalide ions (NCS⁻ or NCO⁻) were synthesized and characterized by infrared spectrometry, electronic absorption spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, elemental analysis, melting points and complexometry with 2,2′,2′′,2′′′-(Ethane-1,2-diyldinitrilo)tetraacetic acid (EDTA). The characterization techniques allowed us to confirm the formation of the copper(II) complexes. The Cu(II) complexes were loaded into microemulsion (MEs) composed of 10% phase oil (cholesterol), 10% surfactant [soy oleate and Brij^® 58 (1:2)] and 80% aqueous phase (phosphate buffer pH = 7.4) prepared by sonication. The Cu(II) complex-loaded MEs displayed sizes ranging from 158.0 ± 1.060 to 212.6 ± 1.539 nm, whereas the polydispersity index (PDI) ranged from 0.218 ± 0.007 to 0.284 ± 0.034. The antibacterial activity of the free compounds and those that were loaded into the MEs against Staphylococcus aureus ATCC^® 25923 and Escherichia coli ATCC^® 25922, as evaluated by a microdilution technique, and the cytotoxicity index (IC₅₀) against the Vero cell line (ATCC^® CCL-81^TM) were used to calculate the selectivity index (SI). Among the free compounds, only compound 2 (MIC 500 μg/mL) showed activity for S. aureus. After loading the compounds into the MEs, the antibacterial activity of compounds 1, 2 and 3 was significantly increased against E. coli (MIC’s 125, 125 and 500 μg/mL, respectively) and S. aureus (MICs 250, 500 and 125 μg/mL, respectively). The loaded compounds were less toxic against the Vero cell line, especially compound 1 (IC₅₀ from 109.5 to 319.3 μg/mL). The compound 2- and 3-loaded MEs displayed the best SI for E. coli and S. aureus, respectively. These results indicated that the Cu(II) complex-loaded MEs were considerably more selective than the free compounds, in some cases, up to 40 times higher.

Theoretical investigations on the molecular structure, vibrational spectra, thermodynamics, HOMO-LUMO, NBO analyses and paramagnetic susceptibility properties of p-(p-hydroxyphenoxy)benzoic acid

The experimental FT-IR (4000-400 cm(-1)) and FT-Raman (3500-100 cm(-1)) spectra of p-(p-hydroxyphenoxy) benzoic acid have been recorded. Quantum chemical calculations of energies, geometries, and vibrational wavenumbers of p-(p-hydroxyphenoxy) benzoic acid (PPHPBA) are carried out using HF and DFT/B3LYP methods with 6-311G (d,p) basis set. The optimized geometrical parameters obtained by B3LYP method show a good agreement with experimental data. The difference between the observed and scaled wave number values of most of the fundamentals is very small. The complete assignments were performed on the basis of the potential energy distribution (PED) of the vibrational modes calculated with scaled quantum mechanical method. The calculated HOMO and LUMO energies allow the calculation of atomic and molecular properties and they also show that charge transfer occurs in the molecule. A detailed molecular picture of PPHPBA and its intermolecular interactions were obtained from NBO analysis. The temperature dependence of various thermodynamic parameters was also studied. The paramagnetic behavior of the molecule under consideration has been investigated and the variation of paramagnetic susceptibility with temperature has been studied.