EPR, ENDOR AND TRIPLE-RESONANCE CHARACTERIZATION OF 3 PARAMAGNETIC REDOX STAGES OF 5-METHYLENE-5H-DIBENZO [A,D]CYCLOHEPTENE

Radical anions and radical trianions derived from 5-methylene-5H-diben zo[a,d]cycloheptene 1, 0-deuterio-5-methylene-5H-dibenzo[a,d]cyclohept ene 1d and 5-dideuteriomethylene-5H-dibenzo[a,d]cycloheptene 1d2 by re duction with lithium, sodium, potassium and caesium in ethereal solven ts have been studied by EPR, ENDOR and TRIPLE resonance spectroscopy. The spin and charge distribution in 1.- and 1(.3-) are discussed both in terms of HMO-McLachlan and INDO calculations. The energies of the l owest unoccupied molecular orbital (LUMO) and of the next lowest unocc upied molecular orbital (NLUMO) are influenced differently by the stro ng interaction of the supercharged radical trianion with the counter-c ations. A change in the orbital sequence of LUMO and NLUMO was predict ed theoretically for the radical trianion relative to that found for t he radical anion, in accordance with the experimental results. The rad ical cations 1.+, 1d.+ and 1d2.+ obtained via oxidation by AlCl3 in di chloromethane solution were also studied by EPR, ENDOR and TRIPLE reso nance spectroscopy. The experimental results were also interpreted in terms of HMO-McLachlan and INDO methods.