Microwave Assisted Synthesis, Spectroscopic, Thermal and Biological Studies of Some Lanthanide(III) Chloride Complexes with a Heterocyclic Schiff Base

Microwave assisted condensation of salicylaldehyde with 2-amino-3-carboxyethyl-4,5-dimethylthiophene in the absence of solvent was efficiently performed to form a potentially tridentate Schiff base viz., 2-(N-salicylideneamino)-3-carboxyethyl-4,5-dimethylthiophene (HSAT). This compound is versatile in forming well defined complexes with lanthanide(III) chlorides under microwave irradiation in solid state. The spectral data showed that the ligand acted as neutral tridentate with ONO donor sequence towards the lanthanide(III) ions, forming complexes of the type [Ln(HSAT)2Cl3] where Ln = La(III), Ce(III), Pr(III), Nd(III), Sm(III), Eu(III) and Gd(III). The complexes possessed 1:2 metal-ligand ratio. X-ray diffraction studies on the ligand and [La(HSAT)2Cl3] showed that the ligand exists in tetragonal and the complex in orthorhombic crystalline forms. Thermal decomposition study of lanthanum(III) complex was carried out. The complex [La(HSAT)2Cl3] underwent facile transesterification. The ligand and the complexes were screened for their antibacterial activities.