The book is an attempt to study the synthesis of heterocycles with novel chromophores as potential antimicrobial agents. The phthalazine based scaffolds having different heterocyclic chromophores includes diversity with five groups, phthalazine-methoxyacrylates, phthalazine-oxadiazoles, phthalazine-isoxazoles, phthalazine-methoxyacrylate-isoxazoles and phthalazine-triazolothiadiazole and triazolothiadiazines. Further, 114 compounds were tested for antimicrobial activity against Esherichia coli, Salmonella typhi, Bacillus subtilis and Staphylococcus aureus. The thiazole and pyridine substituted derivatives shows better activity. All the compounds were thoroughly characterized with all possible physic-chemical techniques.