Definition: In this task, you're given a paragraph from the research paper and your task is to generate a suitable title for the research paper based on the given paper. Under 100 words is a good title length.
Input: Objectives: To synthesize new transitional metal complexes derived from 3-aryl-azo-4-hydroxy coumarin analogues and to evaluate their antimicrobial activities. Methods: The syntheses of complexes of coumarin analogues were accomplished by mixing a hydro-alcoholic solution of 3-aryl-azo-4-hydroxy coumarin analogues with transition metal chlorides. The structural environment of the synthesized molecules was characterized using different instrumental methods. The antimicrobial activity of the compounds was determined by the agar well diffusion method. Results: The cobalt complexes of (E)-3-((4-chlorophenyl) diazenyl)-4-hydroxy-2H-chromen-2-one (HL 1 ): (4a) and (E)-3-((4-methoxyphenyl) diazenyl)-4-hydroxy-2H-chromen-2-one (HL 2 ): (4e) showed excellent antimicrobial activities compared with their ligands. The reports of the antimicrobial investigation showed that the cobalt complexes of 3-aryl-azo-4hydroxy coumarin analogues exhibited potential antimicrobial activity that was stronger than that of their ligands.

Antimicrobial activity of novel synthesized coumarin based transitional metal complexes