Intramolecular dimer radical anions of [3n] cyclophanes: transannular distance dependent stabilization energy.

Intramolecular dimer radical anions of [3n]cyclophanes generated by gamma-ray irradiation in low-temperature glassy matrices showed an absorption band attributable to charge resonance around 936-1210 nm, from which the stabilization energy of the dimer radical anions were analyzed on the basis of pi-electron delocalization over two benzene rings and the damping factor (beta) was estimated to be 0.35 A(-1), which is smaller than that of the intramolecular dimer radical cation of [3n]cyclophanes, indicating a effective charge delocalization of the dimer radical anions.