RESUMO
Imide-fused [n]phenacenes (nPDIs, n = 3, 5, 7) were systematically synthesised and their electronic features were investigated by electrochemical and electronic spectral measurements. nPDIs showed two reduction waves attributed to formation of radical ions and dianions. 3PDI produced blue fluorescence independent of solvent polarity. In contrast, 5PDI and 7PDI displayed marked positive solvatofluorochromism due to intramolecular charge transfer characters between the imide moieties and phenacene π cores in the excited state. The spectral features were analyzed by the Lippert-Mataga relationship and theoretical calculations.
RESUMO
Picene derivatives incorporating imide moieties along the long-axis direction of the picene core (C n -PicDIs) were conveniently synthesized through a four-step synthesis. Photochemical cyclization of dinaphthylethenes was used as the key step for constructing the picene skeleton. Field-effect transistor (FET) devices of C n -PicDIs were fabricated by using ZrO2 as a gate substrate and their FET characteristics were investigated. The FET devices showed normally-off n-channel operation; the averaged electron mobility (µ) was evaluated to be 2(1) × 10-4, 1.0(6) × 10-1 and 1.4(3) × 10-2 cm2 V-1 s-1 for C4-PicDI, C8-PicDI and C12-PicDI, respectively. The maximum µ value as high as 2.0 × 10-1 cm2 V-1 s-1 was observed for C8-PicDI. The electronic spectra of C n -PicDIs in solution showed the same profiles irrespective of the alkyl chain lengths. In contrast, in thin films, the UV absorption and photoelectron yield spectroscopy (PYS) indicated that the lowest unoccupied molecular orbital (LUMO) level of C n -PicDIs gradually lowered upon the elongation of the alkyl chains, suggesting that the alkyl chains modify intermolecular interactions between the C n -PicDI molecules in thin films. The present results provide a new strategy for constructing a high performance n-channel organic semiconductor material by utilizing the electronic features of phenacenes.
