Substitution Effects of C-C Triple Bonds on Deactivation Processes from the Fluorescent State of Pyrene Studied by Emission and Transient Absorption Measurements

摘要

Pyrenes substituted withtert-butylethynyl, trimethylsilylethynyl, and trimethylsilylbutadiynyl groups were prepared, and the fluorescence yields (Φf), lifetimes, and triplet-triplet absorption were measured in cyclohexane. Upon introduction of the groups possessing triple bond(s) to the pyrene skeleton, the fluorescence rate (kf) increased. The variation of the terminating groups did not appreciably affect theΦfandkfvalues. Increasing the number of the triple bond, thekfvalues increased by the magnitude of order whereas theΦfwere not varied. The effect of the ethynyl groups on thekfvalues was rationalized by the Strickler-Berg equation considering an increase of the1Latransition moment. Triplet-triplet absorption spectra of pyrene derivatives were obtained. The intersystem crossing rates (kisc) increased upon increasing the number of triple bonds terminated with the trimethylsilyl group whereas those between ethynylpyrenes were independent of the terminating groups. Heavy atom effect failed to rationalize the enhancement of thekiscvalues upon adding the triple bond to the pyrene moiety.