Acenaphto[1,2-k]fluoranthene: Role of the Carbon Framework Transformation for Tuning Electronic Properties

Acenaphtho[1,2-k]fluoranthene (1) is synthesized via tandem cyclization during the dehydrofluorination of 1,4-di(1-naphthyl)-2,5-difluorobenzene (2) on activated γ-Al₂O₃. Presence of residual hydroxyl groups in alumina reduce the yield of target product 1 because of the side hydrolysis of fluoroarenes with the formation a product of partial cyclization, 9-(1-naphthyl)fluoranthen-8-ol (1b). The formation of negative ions (NI) of compounds 1 and 2 in the gas phase is studied by means of dissociative electron attachment (DEA) spectroscopy. Long-lived molecular NIs 1 and 2 are registered at the thermal energies of electrons, and patterns of their fragmentation are established. The adiabatic electron affinities of compounds 1 and 2 are estimated in the Arrhenius approximation and equal 1.17 ± 0.12 and 0.71 ± 0.07 eV, respectively, which agree with data from quantum chemical modeling at the level of the density functional theory (DFT). Electronic transitions for compounds 1 and 2 are studied via optical absorption and fluorescence spectroscopy. Fluorescence quantum yields are measured, and the resulting data are interpreted according to the time dependent DFT. The electrochemical properties of compounds 1, 1b, and 2 are studied via cyclic voltamperometry, and the levels of boundary molecular orbitals are estimated on the basis of their formal potentials of reduction and oxidation.