EPR, ENDOR and TRIPLE resonance characterization of three paramagnetic reduction stages of 5-(9′-fluorenylidene)-5H-dibenzo[a,d] cycloheptene. Radical anions, radical trianions and radical penta-anions

Abstract

5-(9′-Fluorenylidene)-5H-dibenzo[a,d]cycloheptene (1) has been chemically reduced with alkali metals (Li, Na, K, Cs) to the respective radical anions, radical trianions and radical penta-anions, which have been studied by EPR, ENDOR and TRIPLE resonance spectroscopies. The absolute assignment of the proton hyperfine splitting (hfs) to the 10 (11) positions and to positions in the fluorenyl moiety was feasible by synthesizing and studying the reduction of the selectively deuteriated derivatives 2–6. Comparison of the experimental hfs with those calculated by the INDO method provided important information about the structural changes accompanying the reduction.