A series of phenylsulfanyl and aryl carbonyl containing formazan derivatives 4a-4h and 5a-5h were synthesized by coupling of substituted phenylhydrazones with diazonium salts of 2-(phenylthio) benzenamine and 5-chloro-2-benzoylbenzenamine in pyridine. The electronic properties of the new formazans were studied by cyclic voltammetry and UV-vis spectroscopy. Fluorescence emission wavelengths were measured in solution, and fluorescence quantum yields and Stokes shifts were calculated. Computational studies were carried out on the tautomer structures formed through intramolecular proton transfer in the formazan backbone, and their HOMO-LUMO energy values were estimated. In addition, the influences emerging from ether, thioether and carbonyl groups on the properties of formazans were elaborated.