Theoretical investigation on the crystal structures and electron transfer properties of cyanated TTPO and their selenium analogs

We designed a series of 5,6,7-trithiapentacene-13-one (TTPO) derivatives (from 1 to 20) by attaching cyano groups (-CN) and by replacing S atoms with Se. The incoherent charge-hopping model combined with the Marcus-Hush electron transfer theory were used to evaluate the charge mobility of the title compounds as potential n-type organic field-effect transistors (OFETs) candidates. Based on the optimized face-to-face dimers, the crystal structures were predicted. The replacement of S with Se can decrease the electron reorganization energy (lambda (-)). The introduction of -CN can decrease the energy levels of both HOMOs and LUMOs, which increases the stability. According to the electronic affinities (EA) and structures of dimers predicted by the DFT method coupled with dispersion corrections (-D), we selected compounds 2, 14, 15, and 19 as initial well-performance OFETs materials and predicted their crystal structures. Based on the optimized crystal structures, the charge (both electron and hole) transport mobilities are estimated. Electron mobilities of 14 and 15 are as high as 2.32 and 2.48 cm(2) V-1 s(-1), respectively, indicating that 14 and 15 are the promising n-type OFETs materials. What's more, the predicted crystals show remarkable anisotropic charge mobilities. The maximum electron mobility appears along the direction of face-to-face pi-stacking.