Synthesis, characterization, and theoretical studies of Co(II) and Cu(II) complexes of 1-[(5-mercapto-[1,3,4]thiadiazol-2-ylimino)-methyl]-naphthalen-2-ol and its interaction with Cu nanoparticles

The electronic absorption spectra of Schiff base namely 1-[(5-mercapto-[1,3,4]thiadiazol-2-ylimino)-methyl]-naphthalen-2-ol (H2L) was studied in organic solvents of different polarity as well as in universal buffer solutions of varying pH values at room temperature; the pKa values were calculated. The effect of Co(II) and Cu(II) ions on the electronic absorption spectra of H2L was also assigned and the stability constants of the complexes were calculated. The stoichiometry of the metal complexes was determined spectrophotometrically. Solid Co(II) and Cu(II) complexes with H2L have been synthesized and characterized on the basis of elemental analyses, molar conductance, magnetic susceptibility measurements, IR, electronic as well as ESR spectral studies. The thermal decomposition of the metal complexes was studied by TGA and DTA techniques. The thermo-kinetic parameters; activation energy, pre-exponential factor and entropy of activation were estimated. The interaction between the Schiff base under investigation and the copper nanoparticles in the ground and excited state was considered. The fluorescence quenching rate constant of Schiff base by Cu nanoparticles has a large value.