Synthesis, characterization and theoretical calculations of some Mn(II), Zn(II) and Cd(II) macrocyclic Schiff base complexes containing 2-hydroxy-5-methylisophthaldehyde

Abstract

Two new branched hexadentate amines, 4,7- bis (2-pyridylmethyl)-4,7-diazaundecane-1,10-diamine (L5) and 5,8-bis(2-pyridylmethyl)-5,8-diazadodecane-1,12-diamine (L6), have been synthesized. Condensation with 2-hydroxy-5-methylisophthalaldehyde in the presence of manganese(II), zinc(II) and cadmium(II) ions in methanol leads to produce six new Schiff base macrocyclic complexes [MSb1]2+ and [MSb2]2+ with two 2-pyridylmethyl pendant arms. The resulting compounds were characterized by IR, elemental analysis, Mass and by 1H and 13C NMR in the case of Cd(II) and Zn(II). These compounds are quite stable in air and can be stored in a desiccator for long periods without decomposition. The calculated structure for complexes [MSb2](ClO4), (M=Mn2+, Zn2+ and Cd2+), in the gas phase agrees well with the structure determined [1:1] by Mass and conductivity measurements. The [2+2] complexes are not a simple dimeric form of the [1+1] complexes, because in the former complexes two metal ions are located in a large cavity close to each other, but in two [1+1] complexes they are included in two separate and small cavities. Thus in most cases, depending on the size and the nature of metal ion, the formation of only one of above products will be favorable. The synthesized complexes were screened for their antibacterial activities against four bacterial; (Escherichia coli) PTcc 10009,) Bacillus cereus (ATCC 7064,) taphylococcus subrogation (Lio) و Staphylococeus aureus (ATCC 6633, strains and the complexes showed antibacterial effects.

Keywords

• 2-hydroxy-5-methyl isophthaldehyde
• polyamine ligand
• schiff base complex
• theoretical studies
• antibacterial properties