Mono and binuclear cobalt(II) mixed ligand complexes containing 1,10-phenanthroline and adenine using 1,3-diaminopropane as a spacer: synthesis, characterization, and antibacterial activity investigations

Atakilt Abebe,Wolfgang Linert,Minale Belay,Madhu Thomas,Yosef Bayeh,Tesfay Gebretsadik

doi:10.1186/s43094-020-00030-4

Abstract

BackgroundCoordination compounds, in particular cobalt(II) mixed ligand complexes containing 1,10-phenantroline, have drawn the attention of many investigators as some of them are showing antimicrobial activities.ResultHerein, we report three novel mixed ligand complexes of cobalt(II) having the formulae [Co(L1)2(H2O)2]Cl2, [Co(L1)2(L2)(H2O)]Cl2 and [Co2(L1)4(L2)2(L3)]Cl4 (L1 = 1,10-phenanthroline, L2 = adenine, L3 = 1,3-diaminepropane) were synthesized and characterized by elemental analysis, conductivity measurement, infrared, and UV-Vis spectroscopic techniques. Octahedral geometries are proposed to all the complexes. In vitro antibacterial activities of the ligands, salt, and metal complexes were tested on four pathogenic bacteria (Staphylococcus aureus, Salmonella typhus, Escherichia coli, and Staphylococcus epidermis) using disc diffusion method.ConclusionsIt is interesting to note that the newly synthesized cobalt(II) complexes are active against gram negative bacteria (Escherichia coli and Klebsiella pneumoniae) even though cobalt(II) complexes are well known for their activity against gram positive bacteria.

Highlights

Coordination compounds, in particular cobalt(II) mixed ligand complexes containing 1,10-phenantroline, have drawn the attention of many investigators as some of them are showing antimicrobial activities
Synthesis and characterization studies The formation of the complexes can be represented by the following equations: CoCl2.6H2O + 2L1 → [Co(L1)2(H2O)2]Cl2 (1) [Co(L1)2(H2O)2]Cl2 + L2 → [Co(L1)2L2H2O]Cl2 (2) [Co(L1)2L2H2O]Cl2 + L3 → [Co2(L1)4(L2)2(L3)]Cl4 (3) where L1 = 1,10-phenantroline, L2 = Adenine, and L3 = 1,3-diaminopropane
All the synthesized complexes are soluble in most polar solvents like acetonitrile, DMSO, and water and insoluble in almost all non-polar solvents

Summary

Introduction

Coordination compounds, in particular cobalt(II) mixed ligand complexes containing 1,10-phenantroline, have drawn the attention of many investigators as some of them are showing antimicrobial activities. On coordination with suitable ligands, it is possible to impose a set of desired properties on transition metals for specific applications. It is achieved by altering properties such as the stability of different oxidation states, solvophilicity, electrophilic, and nucleophilic properties of the metal ions. Its exocyclic amino group is less likely to coordinate since the lone pair of electrons is largely delocalized into the ring by resonance (Fig. 3). Because it is free from resonance and steric hindrance, the best coordination site for adenine is N7 of the imidazole ring [38]

Methods

Results

Conclusion