Azaindolo[3,2,1‐jk]carbazoles: New Building Blocks for Functional Organic Materials

Abstract

The preparation and characterization of 12 azaindolo[3,2,1‐ jk ]carbazoles is presented. Ring‐closing C−H activation allowed for the convenient preparation of six singly and six doubly nitrogen‐substituted indolo[3,2,1‐ jk ]carbazole derivatives in which ten of the materials have not been described in the literature before. The detailed photophysical and electrochemical characterization of the developed materials revealed a significant impact of the incorporation of pyridine‐like nitrogen into the fully planar indolo[3,2,1‐ jk ]carbazole backbone. Furthermore, the nitrogen position decisively impacted intermolecular hydrogen bonding and thus the solid‐state alignment. Ultimately, the versatility of the azaindolo[3,2,1‐ jk ]carbazoles scaffold makes this class of materials an attractive new building block for the design of functional organic materials.

The phase transitions of 4-aminopyridine-based indolocarbazoles: twinning, local- and pseudo-symmetry

“…The molecules under investigation were synthesized by ring closure of 9-(2-bromophenyl)-9H-carbazole derivatives with the appropriate N-substitution patterns using 5 mol% of an allyl[1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene]chloropalladium(II) catalyst. Reaction optimization studies and full characterizations are given by Kader et al (2019). Crystals were grown by slow evaporation of acetonitrile solutions.…”

Thienopyrrolocarbazoles: New Building Blocks for Functional Organic Materials

“…[17][18][19] A convenient synthetic approach towards ICz based on C-H activation renders the widespread application of this particular moiety possible. 17,20,21 ICz can be considered a fully planarized derivative of triphenylamine (TPA) and phenylcarbazole (PCz)triarylamine building blocks which are widely employed as electron donors. 22 However, stepwise planarization of TPA decreases the electron donating properties of the triarylamine as the lone pair of the central nitrogen is incorporated into the aromatic system of one (PCz) or two (ICz) pyrrole rings (Scheme 1) and induces light electron accepting properties.…”

“…29 Therefore, we developed a series of nitrogen substituted ICz derivatives (NICz, Scheme 1) and were able to tune the energy levels of the highest occupied molecular orbitals (HOMOs) and lowest unoccupied molecular orbitals (LUMOs) over a wide range. 21 Inspired by these results we set out, to reverse the effect of increased electron deficiency by incorporation of sulfur atoms into the ICz scaffold. Substitution of one benzene ring by thiophene should increase the electron donating power and the HOMO level of the annulated system, yet retaining planarity, which is an important feature for intermolecular interactions and the overall alignment and thus interaction of individual molecules in the solid state.…”

“…Notably, the incorporation of a thiophene subunit decreases the bandgap of the ICz scaffold, which is the opposite effect of nitrogen incorporation, reported previously by our group. 21 Therefore, the presented thienopyrrolocarbazoles are a valuable addition to the toolbox of ICz based building blocks for functional organic materials broadening the scope of this particular class of materials.…”

“…Strikingly, this tendency constitutes an ideal complementation for the nitrogen substitution, which generally lowers the HOMO energy level. 21 Consequently, the development of the thienopyrrolocarbazole series allows to tune the HOMO energy levels of the ICz based building blocks over a wide range of 0.95 eV, which is of tremendous importance for the design of new materials with tailor made molecular properties. Owing to a smaller bandgap of the thienopyrrolocarbazoles, the LUMO levels of the target molecules at -2.38 eV(7), -2.28 eV (8) and -2.30 eV (9) are comparable to that of ICz (-2.27 eV).…”