Ethynyl and Ethenyl Ferrocenyl Dyads with Acridine, Acridone, and Anthraquinone

Ethynylferrocenyl derivatives of 2,7-acridine (1, 2), 9-N-acridone (4), and 2-anthraquinone (6) are described. (Z)-10-(2-iodo-1-ethenylferrocene)-9(10H)-acridinone (3), an intermediate in the formation of 4, N-Fc(CH2)n-acridone (5; n = 8, 11), 1-Fc-anthraquinone (7), and (E)-(2-FcCC)-anthraquinone (8) were also investigated. The X-ray structures of 3 and 6 were determined. B3LYP calculations, UV/vis spectroelectrochemistry, cyclic voltammetry, and ESR spectra were used to probe the ground and excited states of both the neutral and oxidized compounds. Emission is observed from oxidized, but not neutral, 4 and 6; however, 1, 2, and 8 are fluorescent. Surprisingly, emission is reduced upon oxidation of 2 and 8, which appears to correlate with the greater distortion in the excited compared to ground states.