POLYCYCLIC BIS(HYDRAZINE) AND BIS(HYDRAZYL) RADICAL CATIONS - HIGH AND LOW INNER-SPHERE REORGANIZATION ENERGY ORGANIC INTERVALENCE COMPOUNDS

Four-sigma-bond-linked bis(hydrazine) radical cations s3.+, a3.+, and a8.+ show broad visible absorption bands with lambda(max) = 512-548 nm in CH3CN at room temperature, attributed to Hush-type charge-transfer bands (transition energies E(op) = 52.2-55.8 kcal/mol). The correspon ding bis(hydrazyl) radical cations s2.+, a2.+, and a7.+ show near-IR a bsorption with lambda(max) = 1062-1199 nm (E(op) = 26.9-29.3 kcal/mol) . The large difference in E(op) is caused by inner-sphere reorganizati on energy differences, which are predicted well by AM1 semiempirical m olecular orbital calculations. Hush analysis of the absorption bands p roduces electronic coupling matrix elements J = 3.5 +/- 0.5 kcal/mol f or these species, and Marcus-Hush theory predicts intramolecular elect ron-transfer rate constants which are consistent with the experimental observation that ET is slow on the ESR time scale for the hydrazines and fast for the hydrazyls. The bis-inner hydrazyl radical cation 13. exhibits a near-IR absorption band at lambda(max) = 850 nm which is n arrower than those of 2.+ and 7.+ and is concluded not to be a Hush-ty pe charge-transfer band.