Annulation of Tetrathiafulvalene to the Bay Region of Perylenediimide: Fast Electron-Transfer Processes in Polar and Nonpolar Solvents

Abstract

A tetrathiafulvalene donor has been annulated to the bay region of perylenediimide through a 1H-benzo[d]pyrrolo[1,2-a]imidazol-1-one spacer affording an extended π-conjugated molecular dyad (TTF−PDI). To gain insight into its ground- and excited-state electronic properties, the reference compound Ph-PDI has been prepared via a direct Schiff-base condensation of N,N′-bis(1-octylnonyl)benzoperylene-1′,2′:3,4:9,10-hexacarboxylic-1′,2′-anhydride-3,4:9,10-bis(imide) with benzene-1,2-diamine. Both the experimental and the computational (DFT) results indicate that TTF−PDI exhibits significant intramolecular electronic interactions giving rise to an efficient photoinduced charge-separation process. Free-energy calculations verify that the light-induced process from TTF to the singlet-excited state of PDI is exothermic in both polar and nonpolar solvents. Fast adiabatic electron-transfer processes of a compactly fused, π-conjugated TTF−PDI dyad in benzonitrile, 2-methyltetrahydrofuran, anisole and toluene were observed by femtosecond transient absorption spectral measurements. The lifetimes of radical-ion pairs slightly increase with decreasing the solvent polarities, suggesting that the charge-recombination occurs in the Marcus inverted region. By utilizing the nanosecond transient absorption technique, the intermolecular electron-transfer process in a mixture of TTF-diamine/Ph-PDI has been observed via the triplet excited PDI for the first time.