PHOTOINDUCED ELECTRON-TRANSFER REACTION OF PYRAZOLINE DERIVATIVES - FORMATION OF REARRANGEMENT PRODUCT

The initial process of photoinduced electron transfer (PET) between el ectron deficient sensitizers and -substituted-phenyl)-3,5,5-trimethyl- 1-pyrazolines 1 was investigated. Fluorescence quenching rate constant s of the sensitizers by 1 and PET decomposition quantum yields of 1 re flect that the stability of the generated radical cations of 1 and the back-electron transfer play important roles in the reactivity. The ge nerated radical cations of 1 followed by nitrogen elimination gave cyc lopropane derivatives 2 and/or aryl migrated olefins 3. Product distri butions between the cyclopropanes 2 and the olefins 3 depend on the pa ra-substituent of the phenyl ring of 1. Semiempirical MO calculations (AM1) of the radical cations of 1 suggest the location of the spin and the charge governing the product distribution.