TIME-RESOLVED STEP-SCAN FOURIER-TRANSFORM INFRARED-SPECTROSCOPY OF TRIPLET EXCITED DUROQUINONE IN A ZEOLITE

The infrared spectrum of triplet excited duroquinone occluded in zeoli te NaY has been recorded by time-resolved Fourier transform-infrared s pectroscopy on the nano- and microsecond time scale. A commercial step -scan instrument whose capability was expanded to allow absorption spe ctroscopy at nanosecond resolution was employed for this study. O-18 i sotope labeling allowed assignment of a strong absorption at 1542 cm(- 1) to the CO stretching mode. The 100 cm(-1) red shift of this band re lative to the CO stretch of the ground state establishes the pi pi ch aracter of the lowest triplet state of duroquinone. This is consistent with the highly polar environment of the zeolite NaY cage. The lifeti me of the excited triplet state is 20 mu s (-50 degrees C). This const itutes the first time-resolved infrared spectrum of a transient molecu le in a zeolite.