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.
Highlights
Many materials based on these building blocks have been developed for applications in organic light-emitting diodes (OLEDs),[2,7,8,9,10,11,12] organic field-effect transistors (OFETs),[1,2,6,7,13,14,15] organic photovoltaics (OPVs),[2,16,17,18,19] and sensing technology,[11,20,21,22] to name a few
We opted to investigate different approaches for the synthesis of these precursors (Scheme 1). These different strategies allow for the convenient synthesis of the required precursors and pave the way for the future preparation of substituted nitrogen-substituted ICzs (NICzs) as well as for the incorporation of the NICz moiety into larger p-conjugated systems
We have described the convenient synthesis of all six possible mono-substituted azaindolo[3,2,1-jk]carbazoles as well as three symmetric doubly substituted derivatives and their unsymmetrical regioisomers
Summary
The development of p-conjugated small molecules with tailored molecular properties has been one of the major driving forces for the rapid development of the field of organic electronics over the last decades.[1,2] In particular, small to medium sized polycyclic (hetero)aromatic molecules with a defined molecular structure are of tremendous importance.[2,3,4,5,6] many materials based on these building blocks have been developed for applications in organic light-emitting diodes (OLEDs),[2,7,8,9,10,11,12] organic field-effect transistors (OFETs),[1,2,6,7,13,14,15] organic photovoltaics (OPVs),[2,16,17,18,19] and sensing technology,[11,20,21,22] to name a few. There is an ongoing quest for novel fused aromatic moieties to fulfill the requirements of the respective technological application.[2,3,12]. Arylamines are widely employed as electrondonating moieties, reports on the application of ICz have been scarce for a long time,[27,28,29] owing to the elaborate preparation of the planarized scaffold (e.g., vacuum flash pyrolysis).[30,31]
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