Polymeric and sandwich Schiff’s bases complexes derived from 4,4′-methylenedianilineCharacterization and thermal investigation

Cobalt(II), nickel(II) and copper(II) complexes of Schiff’s bases derived from 4,4′-methylenedianiline and pyridine-2-carboxaldehyde(L1), furan-2-carboxaldehyde(L2) or thiophene-2-carboxaldehyde(L3), were prepared and characterized by different analytical and spectral methods. The Schiff bases behave as neutral tetradentate ligands. The chloro-complexes of (L2) with (2:3) mole ratio have a polymeric nature. However, that of L1 and L3 with (1:1) mole ratio showed a sandwich structure. All complexes display an octahedral geometry, except complex (2) which has a tetrahedral one. Oh/Td equilibrium for chloro-complexes of cobalt with ligand L1 was established in the solid state. ESR spectra of solid copper(II) complexes showed isotropic and axial type with dx2-y2 ground state. The thermal study showed that the complexes with different solvents of crystallization exercise different types of interaction. The observed thermochromic phenomenon for cobalt complex was explained along with its thermal behaviour.