Palladium complexes with hexamethyl tetraazacyclotetradecadiene (L) and isomers of its reduced form (‘tet-a’ & ‘tet-b’): synthesis, characterization and antimicrobial studies

Abstract

The hexamethyl tetraazacyclotetradecadiene dihydroperchlorate Me6[14]diene. 2HClO4 (L·2HClO4) on reduction produced two isomeric C- chiral ligands ‘tet-a’ and ‘tet-b’. Reactions of these isomeric ligands with PdCl2 produced square planar tetrachlorodipalladium(II) complexes, [PdL′][PdCl4] (L′ = ‘tet-a’ or ‘tet-b’). Similar reactions of L·2HClO4 with different palladium(II) salts, K2Pd(SCN)4, K2PdBr4 and K2PdI4 produced octahedral palladium(IV) thiocyanato, bromido and iodido complexes. Tetrachlorodipalladium(II) complex of isomeric ligands [PdL′][PdCl4] underwent substitution reactions with KCNS and KNO2 to form tetrathiocyanato dipalladium(II) and tetranitrodipalladium(II) complexes, [PdL′][Pd(NCS)4] and [PdL′][Pd(NO2)4] respectively. However the same tetrachloro complexes underwent axial addition reactions with KBr and KI to form dibromidopalladium(IV) dibromide and diiodidopalladium(IV) diiodide complexes, [PdL′][PdBr2]Br2 and [PdL′][PdI2]I2 respectively. The complexes were characterized on the basis of elemental, spectroscopic, magnetochemical and conductometric analysis. The antibacterial and antifungal activities of the ligands and their complexes have been investigated towards different gram positive and gram negative bacteria and fungi.