Effect of π-System Extension on the Ionization Energy of the Planar Blatter Radical: Experimental and Theoretical Studies

Fusion of benzene, naphthalene, and phenalene rings with the D ring of the planar Blatter radical leads to extension of the pi-system and increased spin delocalization. The effect of this pi-extension and the position of the ring fusion on the electronic structure of the radicals was investigated by UV-photoelectron spectroscopy and DFT CAM-B3LYP/6-311G(d,p) method. The experimental data obtained for 3 out of 8 derivatives were correlated with DFT-derived ionization energies.