NANOSECOND LASER PHOTOLYSIS STUDIES OF PHOTOCHROMIC PROCESSES IN PYRRYL FULGIDES

The photochromic process of (1,4-diphenyl-2-methyl-3-pyrryl)-ethyliden e (isopropylidene) succinic anhydride (I) has been examined with nanos econd laser flash photolysis techniques in cyclohexane and acetonitril e respectively. A new transient species was found in the nanosecond ti me domain. The presence of oxygen was shown to be the important factor in elucidating the mechanism of photocyclization of compound I. The m aximum absorption wavelength and lifetime of the transient species are solvent dependent. Both the excited singlet state and the excited tri plet state are involved in the photocyclization process.