Complexation of 5-fluorosalicylic acid with copper(II): A pH-potentiometric, UV–vis spectroscopic, and electron spin resonance study by the two-dimensional simulation of spectra

Spectroscopic (NMR, UV, FT-IR and FT-Raman) analysis and theoretical investigation of nicotinamide N-oxide with density functional theory

The spectroscopic properties of the nicotinamide N-oxide (abbreviated as NANO, C(6)H(6)N(2)O(2)) were examined by FT-IR, FT-Raman, NMR and UV techniques. FT-IR and FT-Raman spectra in solid state were observed in the region 4000-400 cm(-1) and 3500-50 cm(-1), respectively. The (1)H and (13)C NMR spectra were recorded in DMSO. The UV absorption spectrum of the compound that dissolved in water was recorded in the range of 200-800 nm. The structural and spectroscopic data of the molecule in the ground state were calculated by using Density Functional Theory (DFT) employing B3LYP methods with the 6-311++G(d,p) basis set. The geometry of the molecule was fully optimized, vibrational spectra were calculated and fundamental vibrations were assigned on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method and PQS program. The optimized structure of compound was interpreted and compared with the reported experimental values. The observed vibrational wavenumbers, absorption wavelengths and chemical shifts were compared with calculated values. As a result, the optimized geometry and calculated spectroscopic data show a good agreement with the experimental results.

Effect of fluorine position on the coordinating ability of fluorosalicylic acids--an experimental study complemented with computations

The complexation of 3-, 4-, and 6-fluorosalicylic acids (HL) with copper(II) was investigated in aqueous solution by pH-potentiometry combined with UV-visible spectrophotometry, and in 50 v/v % water-methanol mixture by the two-dimensional ESR simulation method. Both methods showed the formation of [CuLH(-1)] and [CuL(2)H(-2)](2-) of high stabilities, and, at low excess of ligand, the ESR-silent mixed hydroxido complex [Cu(2)L(2)H(-3)](-). Further species were also identified by the two-dimensional ESR simulation method: [CuL](+) in the acidic region, the minor dimer [Cu(2)L(2)H(-2)], and the cis and the trans isomers for [CuL(2)H(-2)](2-). The position of the fluorine atom in the aromatic ring had significant effect on the coordination abilities of the ligands, in good correlation with their reported biological activities. It was 3-fluorosalicylic acid, which formed the most stable complexes [CuLH(-1)] and [CuL(2)H(-2)](2-), while the mononuclear complexes with 6-fluorosalicylic acid were found to be the least stable. For the other ligands (including 5-fluorosalicylic acid studied recently), complexes of medium stabilities were formed. For the interpretation of these findings, ab initio and semi-empirical quantum chemical calculations were carried out for the ligand molecules, isolated and surrounded by water molecules, respectively.