Understanding Electron Transport in Disk-Shaped Triphenylene-Tris(naphthaleneimidazole)s through Structural Modification and Theoretical Investigation

Abstract

ABSTRACT. Disk-shaped molecules with large aromatic π-surface are a class of organic semiconductors of which the charge carrier transport properties could be greatly facilitated by preferred intermolecular stacking of the π-surfaces. The optical and electronic properties are not only determined by the core aromatic structure of these disk-shaped molecules, but also strongly dependent on the sidechains, which directly impact the molecular self-assembly behavior in condensed phases. Triphenylene-tris(naphthaleneimidazole) (TP-TNI) is a recently reported ntype semiconductor featuring a large π-core and branched sidechains with an electron transporting mobility reaching 10 -4 cm 2 V -1 s -1 . In order to further improve material performance, a detailed study is needed to understand the dependence of carrier transporting properties on both the core electronic structure and the sidechain. Here we present the detailed synthesis and characterization of a TP-TNI derivative bearing linear sidechains, which has demonstrated a field effect electron transport mobility up to 1.3×10 -3 cm 2 V -1 s -1 . The more than one order improvement of electron transport properties over the branched side chain homologue can be correlated to ordered twisted packing in the thin film, as revealed by in situ variable temperature grazing incidence wide-angle X-ray scattering (GIWAXS) studies. In-depth theoretical understanding of the frontier orbitals, reorganization energies and charge transfer integrals of TP-TNI molecules have provided further insight into the relationship between molecular stacking geometry and charge transporting properties.3

Charge Mobility in Discotic Liquid Crystals

“…An example of this dependence was given by Zhang and coworkers, who studied compounds containing the triphenylenetris(naphthalene imidazole) core, yielding n-type semiconductor DLC [161,162]. They replaced the branched chains with linear ones, measuring a mobility of 1.3 × 10 −3 cm 2 •V −1 •s −1 [162], more than one order of magnitude higher than the one reported for compounds bearing branched chains, confirming that also lateral chains can influence the properties of mesophases. In the same paper, they established through GIWAXS studies that two adjacent molecules in a column are rotated by an angle of 13 • respect to each other.…”

Perinone—New Life of an Old Molecule

“…Zhang et al [48] synthesized a C 3 -symmetric disk-shaped molecule containing a triphenylene core fused with three naphthaleneimide imidazole "arms". The molecule was obtained as an inseparable statistic mixture of cis (symmetric) and trans (asymmetric) isomers, with a ratio of 1:3, (both displaying a good solubility in solvents such as CH 2 Cl 2 and CHCl 3 ) by the condensation reaction between hexaaminotriphenylene (22) and the corresponding naphthalene mono-anhydride (12) bearing an n-alkyl chain [49]. The synthesis scheme is shown in Figure 9.…”

Mesogenic complementary absorbing dyads based on porphyrin and perylene units

“…Since the side chains have little effect on the HOMO and LUMO values of DLCs [62], the alkyl chains were all replaced by methyl groups in the computer simulations to reduce the computational load. Full geometry optimization of the dyad were performed at the density …”