Bistability between π-diradical open-shell and closed-shell states in indeno[1,2-a]fluorene

Mishra, Shantanu; Vilas‐Varela, Manuel; Lieske, Leonard-Alexander; Ortíz, Ricardo; Rončević, Igor; Albrecht, Florian; Frederiksen, Thomas; Peña, Diego; Groß, Leo

doi:10.48550/arxiv.2303.04483

Cited by 4 publications

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“…In the lowest triplet state of cyclobutadiene, both rotationally related orbitals A and B are singly occupied with the same-spin electrons, resulting in a Baird aromatic D 4h geometry (Figure e, bottom). If U is sufficiently large, then the triplet can even become the ground state, as found in some indenofluorenes. , This is analogous to the electronic structure of the 0 UU metalloporphenes (Figure e), which must be spin-polarized. As the frontier bands in 0 U are spatially almost identical, these metalloporphenes have similar electron and hole mobilities.…”

Section: Results and Discussionmentioning

confidence: 74%

Electronic Structure of Metalloporphenes, Antiaromatic Analogues of Graphene

Pavlak,

Matasović,

Buchanan

et al. 2024

J. Am. Chem. Soc.

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Zinc porphene is a two-dimensional material made of fully fused zinc porphyrins in a tetragonal lattice. It has a fully conjugated π-system, making it similar to graphene. Zinc porphene has recently been synthesized, and a combination of rough conductivity measurements and infrared and Raman spectroscopies all suggested that it is a semiconductor (Magnera, T.F. et al. Porphene and Porphite as Porphyrin Analogs of Graphene and Graphite, Nat. Commun.2023, 14, 6308). This is in contrast with all previous predictions of its electronic structure, which indicated metallic conductivity. We show that the gap-opening in zinc porphene is caused by a Peierls distortion of its unit cell from square to rectangular, thus giving the first account of its electronic structure in agreement with the experiment. Accounting for this distortion requires proper treatment of electron delocalization, which can be done using hybrid functionals with a substantial amount of exact exchange. Such a functional, PBE38, is then applied to predict the properties of many first transition row metalloporphenes, some of which have already been prepared. We find that changing the metal strongly affects the electronic structure of metalloporphenes, resulting in a rich variety of both metallic conductors and semiconductors, which may be of great interest to molecular electronics and spintronics. Properties of these materials are mostly governed by the extent of the Peierls distortion and the number of electrons in their π-system, analogous to changes in aromaticity observed in cyclic conjugated molecules upon oxidation or reduction. These results give an account of how the concept of antiaromaticity can be extended to periodic systems.

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Section: Results and Discussionmentioning

confidence: 74%

Electronic Structure of Metalloporphenes, Antiaromatic Analogues of Graphene

Pavlak,

Matasović,

Buchanan

et al. 2024

J. Am. Chem. Soc.

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“…For all observed shapes, the STM maps show six lobes of high orbital density. Observing similar orbital densities points towards the C13 molecules having the same electronic state, despite adopting different geometries (25).…”

Section: On-surface Synthesis Of C 13mentioning

confidence: 84%

The odd-number cyclo[13]carbon and its dimer cyclo[26]carbon

Albrecht,

Rončević,

Gao

et al. 2024

Preprint

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Cyclo[N]carbons (CN) are molecular rings of N carbon atoms. These exotic carbon allotropes are excellent benchmarking systems for testing quantum chemical theoretical methods, and they may be valuable precursors to other carbon-rich materials. Odd-N cyclocarbons, elusive to date, are predicted to be even less stable than even-N ones, and their structures are unknown. Here we report the on-surface synthesis of cyclo[13]carbon, C13. We elucidate its properties by scanning probe microscopy and theoretical modelling. C13 adopts an open-shell configuration with a triplet ground state and a kinked geometry, which shows different degrees of pronunciation related to different degrees of carbene localization. Moreover, we prepare and characterize the C13 dimer, yielding cyclo[26]carbon, demonstrating the potential of cyclocarbons as precursors to novel carbon allotropes.

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Section: On-surface Synthesis Of C13mentioning

confidence: 84%

Characterization of the odd-number cyclo[13]carbon and its dimer C26

Albrecht,

Rončević,

Gao

et al. 2023

Preprint

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Recently, the family of carbon allotropes was expanded by the generation and on-surface characterization of cyclo[N]carbons (CN), molecular rings composed of N carbon atoms. Several even-N cyclocarbons have been structurally characterized [1-5]. Odd-N cyclocarbons, elusive to date, are predicted to be even less stable than even-N ones [6, 7], and to have distorted low-symmetry structures, localized carbene centres and small singlet-triplet gaps [8], making them excellent systems for benchmarking theoretical approaches [9]. Here we report the synthesis and characterization of cyclo[13]carbon, C13, on a NaCl surface. We elucidate its geometry and electronic structure by atomic force microscopy (AFM), scanning tunnelling microscopy (STM), and theoretical modelling. C13 adopts a geometry with a kink that is observed with different degrees of pronunciation indicating different degrees of carbene localization. The ground state is a triplet with 13 electrons in both in-plane and out-of-plane π-system. The extremely high reactivity of odd-N cyclocarbons facilitates the synthesis of larger carbon allotropes, as indicated by the formation of the C13 dimer [8], cyclo[26]carbon.

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Bistability between π-diradical open-shell and closed-shell states in indeno[1,2-a]fluorene

Cited by 4 publications

References 0 publications

Electronic Structure of Metalloporphenes, Antiaromatic Analogues of Graphene

Electronic Structure of Metalloporphenes, Antiaromatic Analogues of Graphene

The odd-number cyclo[13]carbon and its dimer cyclo[26]carbon

Characterization of the odd-number cyclo[13]carbon and its dimer C26

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