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

Dominik Lungerich,Ivana Ivanović‐Burmazović,Michael Ruppel,Thomas Drewello,Jakob Felix Hitzenberger,Matthias Witt,Andreas Görling,Tibor Döpper,Norbert Jux

doi:10.1002/chem.202002638

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.

Highlights

The positive curvature-induced distortion of polycyclic aromatic hydrocarbons (PAHs) from planar to bowl-shaped geometries can be traced back to the 1960s, when Barth and Lawton first synthesized corannulene in a tour de force of 17 steps.[1]
A dissociation leading to the desired CÀC bond formation is termed “cyclization”, and undesired side reactions are referred to as “fragmentation”
The benzoporphyrin parent ion is selected by a quadrupole mass analyzer, with further activation of the parent ions triggered by collision-induced energy transfer in a collision quadrupole inside the mass spectrometer

Summary

Introduction

The positive curvature-induced distortion of polycyclic aromatic hydrocarbons (PAHs) from planar to bowl-shaped geometries can be traced back to the 1960s, when Barth and Lawton first synthesized corannulene in a tour de force of 17 steps.[1] the development of synthetic strategies such as flash vacuum pyrolysis (FVP) for the preparation of tailor-made precursors, which was widely exploited by Scott et al in the 1990s, allowed for the preparation of corannulene in only three steps in an overall yield of 24 %.[2] the contributions of Sygula, Rabideau, and Siegel and co-workers catapulted corannulene from a high-end molecule to a starting material, these days available in kilogram quantities.[3] That said, the rising interest in unprecedented curved PAHs in materials applications[4] has accelerated the development of novel synthetic methodologies immensely.[5] Nowadays, to avoid temperatures of up to 1100 8C, which are often required for FVP,[6] milder strategies towards strained PAHs dominate the synthetic landscape. Our findings were supported by density functional theory (DFT) calculations and additional mechanistical investigations performed by varying the substituents

Results and Discussion

Conclusions

Conflict of interest