Studies on chalcone derivatives: Complex formation, thermal behavior, stability constant and antioxidant activity

•Spectroscopic studies of copper(II):chalcones complexes.•Thermal decomposition of Cu(II) complexes.•Initial geometry optimizations for Cu(II) complexes.•Interaction between chalcones and the surface of copper nanoparticles.•Antioxidant activity of chalcones.

The chalcone 3-[4′-dimethylaminophenyl]-1-(2-pyridyl) prop-2-en-1-one (DMAPP) and 3-(4′-diethylaminophenyl)-1-(2-pyridinyl) prop-2-en-1-one abbreviated as DEAPP have been synthesized and characterized with IR, 1H NMR, 13C NMR spectroscopic techniques as described previously (El-Daly et al., 2008; Gaber et al., 2009; El-Sayed, 2013). By using UV visible spectroscopy method the mole fraction ratio for copper with DMAPP and DEAPP complexes were determined and it was found to be 1:1. The stability constants of this complex have been determined by Job’s method. The stability constant (Kf) of copper with DMAPP and DEAPP complexes in universal buffer pH = 3.2 was determined to be 9.9 × 104 and 5.2 × 104 respectively. The effect of Cu(II) ion on the emission spectrum of the free chalcone is also assigned. Adherence to Beer’s law and Ringbom optimum concentration ranges are determined. The thermal decomposition of the metal complexes is studied by TGA technique. The kinetic parameters like activation energy, pre-exponential factor and entropy of activation are estimated. The structure of complexes was energetically optimized through molecular mechanics applying MM+ force field coupled with molecular dynamics simulation. The bond lengths and bond angles have been calculated to confirm the geometry of the ligands and their Cu(II) complexes. The mode of interaction of the chalcone to copper nanoparticles was studied. The apparent association constants of the colloidal copper nanoparticles:chalcone complexes in solution were evaluated using the spectral method and compared with the formation constant of the Cu(II) chalcone complexes. Antioxidant activity of these chalcones was evaluated by using 1,1′-diphenyl-2-picrylhydrazyl (DPPH) radicals scavenging method, which showed that the antioxidant activity of DMAPP has higher value than the DEAPP. Semi-empirical study results showed that DMAPP have higher dipole moment than DEAPP [1].

Graphical abstractThe interaction between chalcones ligands and colloidal copper nanoparticles may occurred through the carbonyl group as a result of contribution of the other group in intermolecular hydrogen bond with nitrogen atom of pyridinyl group besides the great steric hindrance with hetero ring. TEM image for the complex formation between DEAPP and Cu nanoparticles. The inserted scheme suggests the mode of interaction between DMAPP and DEAPP with the surface of colloidal Cu0.Figure optionsDownload full-size imageDownload as PowerPoint slide