Synthesis, characterization and antibacterial studies of zinc(II) complexes with hexamethyl-tetraazacyclotetradecadiene Me6[14]diene and C-chiral isomers of its reduced analogue

The ligand salt, Me 6 [14]diene·2HClO 4 (L·2HClO 4 ) was prepared by condensation of acetone and ethylene diamine in the presence of perchloric acid. On reduction of this diene ligand salt, L·2HClO 4 with sodium borohydride, the two isomeric ligands, ‘tet-a’ and ‘tet-b’ were produced. The ligands, on reaction with ZnX 2 (X=Cl, ClO 4 , NO 3 or CH 3 COO) and ZnSO 4 produced the corresponding complexes. These complexes have been characterized on the basis of elemental analyses; IR, UV–Vis and 1 H-NMR spectroscopies; magnetic and conductance data. Based on these data, all of the complexes of the diene ligand L, as well as the perchlorate complexes of all of the ligands attained a square-pyramidal arrangement, whereas the complexes of ‘tet-a’ and ‘tet-b’, with X=NO 3 , Cl or CH 3 COO and with ZnSO 4 salt, were octahedral. Moreover, all complexes were monometallic except the nitrato complex, [(ZnL) 2 (µ-NO 3 )](ClO 4 ) 3 which is bimetallic. The structure of [(ZnL) 2 (µ-NO 3 )](ClO 4 ) 3 has been confirmed by X-ray crystallography. In this complex the zinc centres lie within a N 4 O donor set, with the four nitrogen donors from L and one of the oxygen atom stemming from the bridging NO 3 . The complexes show different electrolytic behavior in different solvents. The antibacterial activities of the ligands and complexes towards different phytopathogenic bacteria have been investigated.