Y.S. El-Sayed

Complex formation, thermal behavior and stability competition between Cu(II) ion and Cu0 nanoparticles with some new azo dyes. Antioxidant and in vitro cytotoxic activity

Four triazole and thiadiazole-based azo chromophores namely [(E)-4-((1H-1,2,4-triazol-3-yl)diazenyl)benzene-1,3-diol.(HL(1)), (E)-4-((5-(methylthio)-1H-1,2,4-triazol-3-yl)diazenyl)benzene-1,3-diol.(HL(2)), (E)-4-((1,3,4-thiadiazol-2-yl)diazenyl)benzene-1,3-diol.(HL(3)) and (E)-4-((5-mercapto-1,3,4-thiadiazol-2-yl)diazenyl)benzene-1,3-diol.(HL(4))] were synthesized and characterized by elemental analyses, IR, UV-Vis as well as mass spectroscopy. Cu(II) complexes of the investigated azo dyes have been synthesized and characterized by elemental analyses, IR, electronic and ESR spectra, magnetic susceptibility and thermogravimetric analyses. 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 azodyes to copper nanoparticles was described as coordination mode of charged dye molecules on the colloidal Cu(0) surface through anchoring OH(-) group. The apparent association constants of the colloidal copper nanoparticles azodye complexes in solution were evaluated using the spectral method and compared with the formation constant of the Cu(II) azo complexes. The antitumor and antioxidant activities of the synthesized azo dyes and their Cu(II) azo complexes have been evaluated.

Spectrophotometric and fluorescence quenching studies of the charge transfer complexation of (4-dimethylamino-benzylidene)-(4,6-dimethyl-pyrimidin-2-yl)-amine with some organic acceptors.

The interaction of organic acceptors such as tetrafluoro-1,4-benzoquinone (p-TFQ), tetrachloro-1,4-benzoquinone (p-TCQ), tetrachloro-1,2-benzoquinone (o-TCQ), tetrabromo-1,4-benzoquinone (p-TBQ), tetrabromo-1,2-benzoquinone (o-TBQ) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) with (4-dimethylamino-benzylidene)-(4,6-dimethyl-pyrimidin-2-yl)-amine (SB) as donor is studied spectrophotometrically and fluoremetrically in dichloromethane and trichloromethane. The association constant (K), thermodynamic parameters (ΔG°, ΔH° and ΔS°), oscillator strength (f), transition dipole moment (μ) and stoichiometric ratio are calculated using Benezi-Hildbrands, Job and straight-line methods, respectively. The results reveal that the interaction between the donor and acceptors is due to π-π* transitions by the formation of radical ion pairs. The fluorescence quenching of SB with different organic acceptors is investigated. The results reveal that the fluorescence quenching obeys the static type mechanism via charge transfer complex formation in the ground state. The effect of temperature on the equilibrium constants of the CT complexes is also studied.