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We have recently reported the role of methoxy substitutions on the optoelectronic properties of two new series of carbazole–bridge–carbazole compounds (bridge = carbazole, phenyl) by varying the number of methoxy groups from 0–4 per carbazole unit. Here, we report the effect of molecular shape (linear versus V-shape), number and linking topology of the methoxy-substitutions on the hole-transport properties of these molecules. The results indicate a delicate balance between the positive and negative effects depending on the substitution topology and the nature of the bridge. It is found that, unlike recent findings from our groups, the methoxy substituents in these compounds reduce the hole mobilities due to the enhanced molecular polarity, a detrimental effect which can be importantly reduced by designing linear D–A–D architectures. The differences in the geometries of the new compounds and their hole transport properties as a function of the nature of the bridge, number of methoxy groups and the substitution topology are explained in terms of the different symmetry of HOMO and HOMO−1 of the carbazole units, which interact very differently with the methoxy substituents and the bridge (carbazole or phenyl). The pros and cons of using- versus -avoiding methoxy groups in order to improve the hole mobility of the new compounds are discussed with regard to the targeted application. 

Abstract 2D polymers (2DPs) are promising as structurally well‐defined, permanently porous, organic semiconductors. However, 2DPs are nearly always isolated as closed shell organic species with limited charge carriers, which leads to low bulk conductivities. Here, the bulk conductivity of two naphthalene diimide (NDI)‐containing 2DP semiconductors is enhanced by controllably n‐doping the NDI units using cobaltocene (CoCp₂). Optical and transient microwave spectroscopy reveal that both as‐prepared NDI‐containing 2DPs are semiconducting with sub‐2 eV optical bandgaps and photoexcited charge‐carrier lifetimes of tens of nanoseconds. Following reduction with CoCp₂, both 2DPs largely retain their periodic structures and exhibit optical and electron‐spin resonance spectroscopic features consistent with the presence of NDI‐radical anions. While the native NDI‐based 2DPs are electronically insulating, maximum bulk conductivities of >10⁻⁴ S cm⁻¹are achieved by substoichiometric levels of n‐doping. Density functional theory calculations show that the strongest electronic couplings in these 2DPs exist in the out‐of‐plane (π‐stacking) crystallographic directions, which indicates that cross‐plane electronic transport through NDI stacks is primarily responsible for the observed electronic conductivity. Taken together, the controlled molecular doping is a useful approach to access structurally well‐defined, paramagnetic, 2DP n‐type semiconductors with measurable bulk electronic conductivities of interest for electronic or spintronic devices.