time decay relating to the absorbance is kept remained as the same and the sample has not been deteriorated even after being irradiated of 13000 times by nanosecond uv laser in addition fig1 illustrates the ultraviolet visible absorption spectrum of 7 8 dimethoxy 2 3 4 u2032 5 u2032 tetraphenylspiro imidazo 2 1 u03b1 isoindole 5 2 u2032 imidazole irradiated once by the nanosecond ultraviolet laser and irradiated 13000 times by the nanosecond ultraviolet laser and it confirms that the ultraviolet visible absorption spectrum after the first irradiation and that after 13000 times of irradiation are kept unchanged and the result indicates that 7 8 dimethoxy 2 3 4 u2032 5 u2032 tetraphenylspiro imidazo 2 1 u03b1 isoindole 5 2 u2032 imidazole is a photochromic compound having a high repetition durability the synthesizing processes of the above includes placing 2 1 3 dioxolan 2 yl benzaldehyde 1 00 g 5 61 mmol benzyl 1 21 g 5 76 mmol ammonium acetate 1 59 mg 20 6 mmol and chloroform 8 ml into a sealed tube container then stirring for 18 hours at 110 u00b0 c neutralizing with aqueous ammonia performing an extraction with chloroform drying the organic layer with sodium sulfate and distilling off the solvent under reduced pressure to obtain the crude product and performing a purification with silica gel column chromatography hexane ethyl acetate 2 1 to obtain 2 2 1 3 dioxolan 2 yl phenyl 4 5 diphenyl 1h imidazole 731 mg 1 94 mmol in 81 yield 1 h nmr 400 mhz dmso d 6 u03b4 12 59 s 1h 7 97 7 94 m 2h 7 74 7 70 m 2h 7.