Indolo[3,2,1-jk]carbazole (IC) has been synthesised on a gram scale by flash vacuum pyrolysis. In contrast to a previous suggestion, IC is planar and it is also highly fluorescent, with a solution quantum yield of 0.41. Electro-oxidation of IC at a rotating disc electrode resulted in the passage of steady-state currents and the reproducible formation of conducting, redox-active films with constituent species that are also highly fluorescent. Unusually for coupled electroactive N-heterocyclic systems, electrochemical and spectroscopic characterisation revealed the film to consist exclusively of three redox-active (2,2', 5,5' and 2,5' coupled) IC dimers with no polymeric products. Calculations showed this coupling pattern to be consistent with IC radical-cation coupling through the accessible sites of highest unpaired electron density. The unusual combination of a high dimer second oxidation potential and a negligible dimer-dimer coupling rate explains the lack of further coupling. The identities of the dimeric species were confirmed by independent syntheses involving the Suzuki-Miyaura coupling of IC boronic acids as the key step. Electro-oxidation of the IC system therefore offers a ready route to novel conducting, redox-active molecular films and their redox-active, luminescent dimer constituents.

Flash vacuum pyrolysis (FVP) of N-allyl- or N-benzyldibenz[b,f]azepine at temperatures from 750 to 950 degrees C gives pyrrolo[3,2,1-jk]carbazole as the major product. The mechanism of the ring contraction involves dibenzazepin-1-yl radical formation, followed by transannular attack and formation of a 2-(indol-1-yl)phenyl radical which cyclizes. The mechanism is supported by independent generation of 2-(indol-1-yl)phenyl radicals by two different methods, and the use of 1-(2-nitrophenyl)indole as a radical generator gives an optimized synthetic route to pyrrolo[3,2,1-jk]carbazole (54% overall yield in two steps from indole). The first substituted pyrrolo[3,2,1-jk]carbazoles have been synthesized by FVP methods and also by reactions of the parent compound with electrophiles, leading to a range of 4-substituted pyrrolocarbazoles.

Selectively substituted indolo[3,2,1-jk] carbazole (IC) molecules have been synthesized through flash vacuum pyrolysis (FVP) and then electro-oxidized, resulting in the formation of redox-active and electronically conducting thin films consisting exclusively of three highly luminescent dimer species, the 2,2'-, 2,10'-, and 10,10'-coupled dimers. DFT calculation has enabled both the accurate calculation of monomer oxidation potentials and the prediction of the nature of the resulting dimers through consideration of the coupling of the oxidized monomer radical cations. This demonstrates that substituted ICs represent a class of molecules able to form redox-active and conducting dimer films of controlled composition upon oxidation and that DFT calculations can be used to inform the synthesis of specific IC monomers most likely to both produce electronically conducting thin-film materials and yield specific luminescent dimers with desirable materials properties.

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Flash vacuum pyrolysis of N-(2-nitroheteroaryl)indoles or-carbazoles at 875°C gave aza analogues of strained pyrrolo[3,2,1-jk]carbazole (50-55%) and indolo[3,2,1-jk]carbazole (55-85%) ring systems, respectively, through generation of aryl radicals and cyclization. The corresponding reactions of N-(2-nitroheteroaryl)indazoles and-benzimidazoles at 850°C, on the other hand, gave carbazole-1-carbonitrile derivatives (56-64%) by a mechanism involving radical ring opening and hydrogen atom rearrangement.