Theoretical Investigation on Charge Transfer Properties of 1,3,5-Tripyrrolebenzene (TPB) and its Derivatives with Electron-withdrawing Substituents

Abstract

Abstract:The electronic structures and charge transport properties of 1,3,5-tripyrrolebenzene (TPB) and its substituted derivatives with -F and -CN groups have been investigated by DFT calculations in combination with the Marcus hopping model. The dimer geometry was optimized by density functional theory method with dispersion force correction being included (DFT-D). Consequently, the charge transfer integral was evaluated. The calculation results show that the introduction of electron-withdrawing substituents does not significantly change the bond lengths and molecular symmetry of TPB, but lower the coplanarity between the pyrrole and benzene rings, especially in the case of CN substitution. Meanwhile, the introduction of electron-withdrawing groups can decrease the energy of the frontier molecular orbital and enhance the air stability. Fluorination makes the λe increase obviously while cyanation dose not. Generally speaking, the λe values of the title compounds are larger than their λh. Except for compounds 6 and 9, all others keep the face to face packing or have a slight slip in dimers, but the center of mass distances increase after fluorination or cyanation due to the distortion of the monomer's coplanarity. The predicted quasi-one-dimensional electron mobility of the dimers is up to 0.433 cm 2 ·V -1 ·s -1 at 298.15 K. The electron injection barriers of 2 and 7 are lower than that of TPB. The TPB derivatives of 1, 2, and 7 are potential n-channel materials with the high electron mobility.

Electronic Structures and Mobilities of 2,2'-diphenyl-5,5'-bithiazole Derivatives

“…It can also be seen that the mobilities of difluorinated DPBT are larger than tetra-or hexafluorinated ones, although an increasing number of substituted fluorine lowers the LUMO energies. This result is in agreement with our former findings that a somewhat moderate number of substituted fluorine is beneficial to the electron transfer, [5] instead of lots of substituted fluorine atoms. In addition, electron mobility of 3C is the second largest in Table 1, indicating that the cyano group could also increase the electron mobility in some cases.…”

An In Silico Study on the Isomers of Pentacene: The Case for Air-Stable and Alternative C22H14 Acenes for Organic Electronics

“…Although the 6-31G­(d) and 6-31+G­(d) basis sets have been found to give satisfactory values to experimental observations, − more-complete basis sets such as of 6-311G to 6-311++G­(d,p) are also prevalent throughout the literature − for higher accuracy where needed. We also deploy the 6-311++G­(d,p) basis set, owing to the unknown structures and charge transfer properties of the isomers of pentacene, particularly with regards to the dimer separations of the nonplanar isomers, which do not have experimental observations for comparison with this work.…”