Abstract
Abstract The Schiff base ligands 4-methyl-7-(salicylidineamino) coumarin, HL1 and N1,N2-bis[8-(1-ethylidene)-7-hydroxy-coumarin] 1,2-diamine, H2L2 and their metal complexes M(II), [M(II) = Zn, Cu, Ni, Co, Cd and Pd] have been synthesized and characterized on the bases of elemental analysis, molar conductance and a variety of spectral methods. The molar conductance values revealed that the chelates are nonelectrolytic in nature. IR spectra showed that the Schiff bases are coordinated to the metal ions via an azomethine nitrogen and phenolic oxygen while lactone carbonyl does not participate in the coordination. Other spectral studies suggested tentative structures for the complexes. Single crystal X-ray diffraction of [{Cu(L1)2}2] complex revealed that Cu(L1)2 units are associated into a dimer by rather long Cu…O bond, with a distorted square based pyramidal geometry, within each monomer and the methyl coumarin skeletons are trans to one other. Antimicrobial activity of the free ligands HL1 and H2L2 and their metal complexes has been screened. The studies demonstrated that metallation can increase the antibacterial activity more than the free ligands.
