A new unsymmetrical photochromic diarylethene, 1-(2-methyl-5-phenyl-3-thienyl), 2-(2- methyl-5-(3-methylphenyl)-3-thienyl)-3, 3, 4, 4, 5, 5-hexafluorocyclopent-1-ene (MPMTH), was synthesized and its structure was determined by single-crystal X-ray diffraction analysis. Its optical and electrochemical properties, including photochromic reactivity both in solution and in the crystalline phase, fluorescence and electrochemical property were investigated. ...