Synthesis, Characterization and In vitro Antifungal Activity Studies of Copper(II) Complexes Derived from 6-hydroxyflavone Schiff bases

Bello U., Idris S. O., Shallangwa G. A.

Abstract


This study reported the synthesis of the new ligands (E) – 4 – ((2-hydroxyphenyl)imino)-2-phenyl-4H-chromen-6-o1 (L1), (E) – 2 – ((6-hydroxy-2-phenyl-4H-chromen-4-ylidene)amino)benzaldehyde (L2) and (E) – 2–(6-hydroxy-2-phenyl-4H-chromen-4-ylidene)hydrazinacarbothidanide (L3). These three Schiff base ligands were synthesized by refluxing equimolar amount of 6-hydroxyflavone with 2-aminophenol, 2-aminobenzoic acid and thiosemicarbazide as ligands L1, L2 and L3 respectively. The synthesized Schiff bases were subsequently reacted with copper(II) acetate to form the corresponding metal complexes C1, C2 and C3. The compounds were characterized using FT-IR, Molar conductance, Melting point/decomposition temperature studies, Solubility test and Gravimetric analysis. The purity of the compounds was determined using TLC. The solubility test of the compounds indicated that they are soluble in most organic solvents except acetone, water and tetrachloromethane in which they are completely insoluble. The Schiff base ligands have melting point between 166 – 185 oC, whereas the copper(II) complexes decomposes in the range 161 – 202 oC. Molar conductance values of the complexes measured are low, indicating their non-electrolytic nature. The spectroscopic data indicated that the Schiff base ligands acted as tridentate and coordinated to the metal via imine nitrogen and deprotonated phenolic oxygen atoms. The in vitro antifungal activity of the synthesized ligands and their metal complexes were studied against two fungal species (Aspergillus niger and Candida albicans) and the results indicated that the complexes were more active than the ligands but less active compared to reference drug (fluconazole). 

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