Some new unsymmetrical diimino tetradentate schiff base derived from 3,4-Diaminobenzophenone: Synthesis, characterization and the formation constant of Ni(II) and Cu(II) complexes

Some new unsymmetrical diimino tetradentate Schiff bases derived from 3,4-diaminobenzophenone, (N-salicyliden-N′-5- OMe.salycyliden)-3,4-diaminobenzophenone (H₂sal-5-OMe.sal.dabp) (H₂L¹), (H₂sal-5-Br.sal.dabp) (H₂L²), (H₂sal-5-Cl.sal.dabp) (H₂L³) and (H₂sal-5-NO₂.sal.dabp) (H₂L⁴) and their Ni(II) and Cu(II) complexes were synthesized and characterized by elemental analysis, IR, ¹H NMR, UV-Vis spectra and mass spectra. The thermodynamic formation constants of the complexes were determined spectrophotometrically at constant ionic strength (0.1 M NaClO₄) at 25 °C in DMF and their free energies of formation were calculated at 25 °C.