Synthesis, Characterization and Crystal Structures of Zinc(II) and Cobalt(III) Complexes Derived from Tridentate NNO- and NON- Schiff Bases with Antibacterial Activities

Heng-Yu Qian

doi:10.17344/acsi.2021.6721

Abstract

Two new polynuclear zinc complexes [Zn2Br2(L1)2] (1) and [Zn(μ1,5-dca)L2]n (2), and two new mononuclear cobalt(III) complexes [CoL1N3(Brsal)] (3) and [CoL2(HL2)] (4), where L1 = 5-bromo-2-(((2-dimethylamino)ethyl)imino)methyl)phenolate, L2 = 5-bromo-2-(((2-hydroxyethyl)imino)methyl)phenolate, dca = dicyanoamide, Brsal = 5-bromo-2-formylphenolate, have been synthesized and characterized. The complexes were characterized by elemental analyses, IR, UV-Vis spectra, molar conductivity, and single crystal X-ray diffraction. X-ray analysis indicates that the Zn atoms in complex 1 are in distorted square pyramidal coordination, the Zn atoms in complex 2 are in distorted trigonal bipyramidal coordination, and the Co atoms in complexes 3 and 4 are in octahedral coordination. The molecules of the complexes are stacked through π···π interactions and hydrogen bonds. The complexes were assayed for antibacterial activities against three Gram-positive bacterial strains (B. subtilis, S. aureus, and St. faecalis) and three Gram-negative bacterial strains (E. coli, P. aeruginosa, and E. cloacae) by MTT method.

Highlights

Schiff bases are an important class of organic compounds and a great number of Schiff base compounds have been prepared due to their facile synthesis
In continuation of our work on the exploration of new antibacterial agents, we report the synthesis, characterization including single crystal X-ray structures of two new zinc(II) and two new cobalt(III) complexes, [Zn2Br2(L1)2] (1), [Zn(μ1,5-dca)L2]n (2), [CoL1N3(Brsal)] (3)
The Schiff base ligands coordination is substantiated by the phenolic C–O stretching bands at 1170–1200 cm–1 in the four complexes.[12]

Summary

Introduction

Schiff bases are an important class of organic compounds and a great number of Schiff base compounds have been prepared due to their facile synthesis. These compounds have received considerable attention in pharmaceutical fields because of their excellent biological activities.[1] Schiff bases are a kind of significant ligands in coordination chemistry, which can form versatile structures with interesting biological, magnetic, catalytic and photoluminescent properties.[2] In recent years, much efforts have been paid on zinc and cobalt complexes with Schiff base ligands due to their indispensable application in biological area such as antimicrobial agents.[3] We have reported some manganese and zinc complexes with antibacterial activities.[4] In continuation of our work on the exploration of new antibacterial agents, we report the synthesis, characterization including single crystal X-ray structures of two new zinc(II) and two new cobalt(III) complexes, [Zn2Br2(L1)2] (1), [Zn(μ1,5-dca)L2]n (2), [CoL1N3(Brsal)] (3). The antibacterial activity against three Gram-positive bacterial strains (B. subtilis, S. aureus, and St. faecalis) and three Gram-negative bacterial strains (E. coli, P. aeruginosa, and E. cloacae) by MTT method was studied

Experimental

Results and Discussion

Conclusion