Synthetic, structural and biological properties of binuclear complexes with some Schiff bases.

The complexes of Co(II), Ni(II) and Cu(II) with N,N'-bis-[5-X-salicylidene]-4,4'-diaminodibenzyl, abbreviated as H2-XSalPDADB (X = -H, -CH3, -Br) have been synthesized and investigated by elemental analysis, electrical conductance, magnetic, spectral and thermal studies. The molar conductivity data indicate that the complexes are non-electrolytes. Analytical data support 1:1 (M:L) stoichiometry. The reflectance spectra along with the magnetic data suggest pseudo-tetrahedral geometry for the complexes. The Schiff bases function as tetradentate ligands coordinating through ON-NO donor system. Substitution in the phenyl ring of the complexes produces shift in the azomethine v(C=N) stretching vibrational frequency, which is related to the Hammett's substituent perameter (sigma). The 1H-NMR data reveal that all Schiff bases exist in enol-iminic form. Various ESR parameters for copper complexes have been calculated. The compounds have been screened for their biological activities.