Absorption spectra of dimer cations. Part 4.—Theoretical considerations and dimer structure

Abstract

Theoretical calculations of the energy levels of the cation and anion of 2,2′-paracyclophane and the dimer cations of benzene, (C₆H₆)⁺ ₂, and naphthalene, (C₁₀H₈)⁺ ₂, have been made : the methods are similar to those used for the closely related excimers; a “perfect sandwich” arrangement (D_6h or D_2h respectively) was assumed for the dimers. The calculations support the assignment of the long-wavelength band to a charge resonance transition, but the shifts of monomer bands on dimerization cannot be explained unless distortion of the sandwich arrangement takes place. The stable configurations of dimer cations and the apparent instability of dimer anions are discussed.