Gas‐Phase Transformation of Fluorinated Benzoporphyrins to Porphyrin‐Embedded Conical Nanocarbons

Abstract

Geodesic nitrogen‐containing graphene fragments are interesting candidates for various material applications, but the available synthetic protocols, which need to overcome intrinsic strain energy during the formation of the bowl‐shaped skeletons, are often incompatible with heteroatom‐embedded structures. Through this mass spectrometry‐based gas‐phase study, we show by means of collision‐induced dissociation experiments and supported by density functional theory calculations, the first evidence for the formation of a porphyrin‐embedded conical nanocarbon. The influences of metalation and functionalization of the used tetrabenzoporphyrins have been investigated, which revealed different cyclization efficiencies, different ionization possibilities, and a variation of the dissociation pathway. Our results suggest a stepwise process for HF elimination from the fjord region, which supports a selective pathway towards bent nitrogen‐containing graphene fragments.

Aromatic Ring Fusion to Benzoporphyrin via γ-ortho Cyclodehydrogenation on a Ag(111) Surface

“…43,44 Moreover, the envisaged 8-fold γ-ortho fused product possesses a conical structure, which is suggested to be energetically unfavored compared to the formation of planar competing products. 35,45 In addition, we conducted deposition of TPTBP on hot Ag(111) (660 K). The produced molecular motifs are similar to those obtained via stepwise annealing.…”

“…This hybrid structure is fully aromatic and has up to 66 conjugated π-electrons. Furthermore, it possesses a bowl-shaped structure and is supposed to exhibit interesting optoelectronic properties with potential applications in organic electronics, catalysis, and optics. − Nonetheless, the activation of the γ-positions usually requires harsh conditions, e . g ., temperatures up to 1000 °C, which usually leads to the decomposition of the molecules. , Thus far, the synthesis of γ- ortho fused fully aromatic porphyrins remains challenging, and their electronic structures remain elusive.…”

The Synthesis of Conical Carbon

“…Recently, Lungerich and coworkers reported the formation of porphyrin‐embedded conical nanocarbons through the conversion of fluorinated benzoporphyrins under gas‐phase conditions. [ 79 ] The gas‐phase conversion was realized by collision‐induced dissociation experiments on a mass spectrometer. Although there is sufficient experimental evidence to prove that Lungerich's gas‐phase experiments produced conical nanocarbons, the preparative‐scale synthesis of conical nanocarbons is still underway.…”

Recent Advances in Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds

“…In 2020, Lungerich, Jux, Drewello, and co-workers reported a mass spectrometry-based gas-phase study of a porphyrin-based conical graphene fragment 313.2a – d formed by means of 8-fold fjord region-selective cyclodehydrofluorination ( Scheme 313 ). 587 The γ–ortho cyclization and was found to depend on the choice of metal and functionalized fluorinated meso- aryl porphyrins. The coupling mechanism was presumed to consist of C–C nucleophilic addition followed by 1,2-elimination of HF.…”

“… Reagents and conditions: (a) 587 gas phase, Δ E , N 2 ; (b) Pd(PCy 3 ) 2 Cl 2 (8 equiv), DMAc/DBU (v/v 4:1), MW, N 2 , 180 °C, 4 h. …”