Electronic structure of 2,5,8-tri-tert-butylphenalenyl radical studied by He(I) photoelectron spectroscopy

Phenalenyl radical is an odd-alternant hydrocarbon radical of high symmetry, D3h and is extremely attractive as the constituent of molecular magnets. But it has not been characterized in detail. Recently, 2,5,8-tri-tert-butylphenalenyl radical has successfully been synthesized. In this work the gas phase He(I) photoelectron spectrum of this radical has been measured and analyzed with the aid of UHF MO and RHF MO SECI calculations. The first band has been assigned to the ionization from the SO–π–MO of the neutral radical. The second band group has been ascribed to the ionized states relevant to three triplet ionic states and one singlet ionic state of the monocation, the third band group being ascribed to the two singlet ionic states of the monocation.