Study On The Syntheses And Antibacterial Acticity Of Metal Organic Complexes Built From Three Carboxylate Ligands

Metal-organic coordination polymers based on imidazole, tetrazole and its derivatives have attracted great interest due to their potential applications in optical, magnetic, electrocitric and biological field. In order to explore and obtain the coordination polymers with novel structures and excellent biological activity based on imidazole, tetrazole and its derivatives, twenty one coordintian polymers were synthesized and crystallized via the solution crystallization and hydrothermal method. Including 11 complexes based on 2-ethyl-4,5-imidazolediacarboxylate, 4 complexes built from 2-propyl-4,5–imidazole diacarboxylate and 6 complexes based on 1-H-tetrazole acetic acid in which 4 heterometallic complexes were formed in situ reaction.These complexes were characterized by elemental analysis, IR, thermogravimetric analyses and single crystal X-ray diffraction, in which the ligands exhibit a variety of coordination modes.The ligand exhibit eight different coordination modes in complexes based on 2-ethyl-4,5-imidazolediacarboxylate ligand or 2-propyl-4,5-imidazolediacarboxylate ligand:(1) Chelates the central ion via one imidazole nitrogen atom and one carboxyl oxygen atom (complex 2, 3, 4, 12, 15);(2) Chelates the central ion via one imidazole nitrogen atom and one carboxyl oxygen atom and link another central ion via the other carboxyl oxygen atom of the same carboxylate group (complex 5, 6);(3) Chelates the central ion via one imidazole nitrogen atom and one carboxyl oxygen atom and link another central ion via the carboxyl oxygen from the other carboxylate group (complex 7, 8, 14);(4) Chelates the central ion via one imidazole nitrogen atom and one carboxyl oxygen atom and link another two central ions via the carboxyl oxygen from the other carboxylate group (complex 9);(5) Chelates the central ion via one imidazole nitrogen atom and one carboxyl oxygen atom and links another central ion via the same carboxyl oxygen and connects the third central ion via the carboxyl oxygen atom from the other carboxylate group (complex 10);(6) Chelates the central ion via two carboxyl oxygen atoms and links another central ion via the same carboxyl oxygen and connects the third central ion via the carboxyl oxygen atom from the other carboxylate group (complex 10);(7) Chelates two central ions via two imidazole nitrogen atoms and two carboxyl oxygen atoms (complex 11);(8) Chelates one central ion via one imidazole nitrogen atom and one carboxyl oxygen atom and bridge another central ion via the same carboxyl oxygen atom (complex 13); The ligand exhibits two kinds of coordination modes in complexes built from tetrazole-1-acetate:(1) Chelates one central ion via two carboxyl oxygen atoms and bridges another central ion via one carboxyl oxygen atom and connect the third central ion via one tetrazole nitrogen atom (complex 16);(2) Connects two adjacent central ions via two carboxyl oxygen atoms in mono-dentate and bridges another two central ions via two tetrazole nitrogen atoms in mono-dentate (complex 17).The antibiotic activities of the ligands and 9 complexes were tested against Escherichia coli, Pasteurella, Bacillus cereus bacteria by the microplate method. The result shows that all complexes exhibit antibacterial activity except complex 5, it shows inhibitory effect at low concentration, but with the increasement of the concentration, it shows promoting effect, which differs greatly with the role of ligand. And the mechanism needs further research in future work. Complex 16 exhibits quite strong antibacterial activity against all three tested bacteria with the MIC of 312μg/mL, 312μg/mL and 625μg/mL, respectively. Complex 6 also exhibits strong antibacterial activity against Escherichia coli and Bacillus cereus with MIC of 312μg/mL and 625μg/mL, respectively.