Synthetic tuning of the quantum properties of open-shell radicaloids

Lombardi, Federico; Ma, Ji; Alexandropoulos, Dimitris I.; Komber, Hartmut; Liu, Junzhi; Myers, William K.; Feng, Xinliang; Bogani, Lapo

doi:10.1016/j.chempr.2021.03.024

Cited by 11 publications

(8 citation statements)

References 82 publications

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“…Thus, the synthesis toward π‐extended 2 and 3 through the similar synthetic strategies was carried out. Compounds 2‐(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)isophthalaldehyde ( 10 ), [21] 4‐chlorophenanthrene ( 11 ) [22] and 5‐bromochrysene ( 13 ) [5b] were firstly synthesized through multi‐step procedures. Subsequently, 2‐(phenanthren‐4‐yl) isophthalaldehyde ( 12 ) or 2‐(chrysen‐5‐yl) isophthalaldehyde ( 14 ) were synthesized by Suzuki coupling of 11 or 13 with 10 in 34 % and 70 % yield, respectively.…”

Section: Figurementioning

confidence: 99%

Benzo‐Extended Cyclohepta[def]fluorene Derivatives with Very Low‐Lying Triplet States

Lombardi

et al. 2022

Angewandte Chemie

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Open‐shell non‐alternant polycyclic hydrocarbons (PHs) are attracting increasing attention due to their promising applications in organic spintronics and quantum computing. Herein we report the synthesis of three cyclohepta[def]fluorene‐based diradicaloids (1–3), by fusion of benzo rings on its periphery for the thermodynamic stabilization, as evidenced by multiple characterization techniques. Remarkably, all of them display a very narrow optical energy gap (Egopt=0.52–0.69 eV) and persistent stability under ambient conditions (t1/2=11.7–33.3 h). More importantly, this new type of diradicaloids possess a low‐lying triplet state with an extremely small singlet–triplet energy gap, as low as 0.002 kcal mol−1, with a clear dependence on the molecular size. This family of compounds thus offers a new route to create non‐alternant open‐shell PHs with high‐spin ground states, and opens up novel possibilities and insights into understanding the structure–property relationships.

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Section: Figurementioning

confidence: 99%

Benzo‐Extended Cyclohepta[def]fluorene Derivatives with Very Low‐Lying Triplet States

Lombardi

et al. 2022

Angewandte Chemie

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“…[4] Moreover, the topological transformation induced by these non-alternant moieties could also determine the electronic ground state of NGs, [5][6][7][8][9][10][11][12][13][14][15] affording the potential open-shell character and promising applications in organic spintronics. [16,17] As a representative example, pyrene (a) can be transformed into one of its non-alternant isomers, that is, cyclohepta[def]fluorene (b) (namely bis-periazulene), by replacing the inner naphthalene unit with azulene (Figure 1a), which is predicted to be an open-shell Kekulé structure with a low triplet ground state. [18] However, the synthesis of cyclohepta[def]fluorene (b) and its derivatives is quite challenging owing to their intrinsic instability.…”

Section: Introductionmentioning

confidence: 99%

“…Among them, the introduction of non‐alternant units (i. e., azulene or heptalene) into non‐benzenoid NGs could cause local changes in strain and molecular symmetry, thus significantly impacting their physicochemical properties [4] . Moreover, the topological transformation induced by these non‐alternant moieties could also determine the electronic ground state of NGs, [5–15] affording the potential open‐shell character and promising applications in organic spintronics [16,17] . As a representative example, pyrene ( a ) can be transformed into one of its non‐alternant isomers, that is, cyclohepta[ def ]fluorene ( b ) (namely bis‐periazulene), by replacing the inner naphthalene unit with azulene (Figure 1a), which is predicted to be an open‐shell Kekulé structure with a low triplet ground state [18] .…”

Section: Introductionmentioning

confidence: 99%

Structural Expansion of Cyclohepta[def]fluorene towards Azulene‐Embedded Non‐Benzenoid Nanographenes

Barragán

Gallardo

et al. 2023

Chemistry A European J

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Non‐benzenoid non‐alternant nanographenes (NGs) have attracted increasing attention on account of their distinct electronic and structural features in comparison to their isomeric benzenoid counterparts. In this work, we present a series of unprecedented azulene‐embedded NGs on Au(111) during the attempted synthesis of cyclohepta[def]fluorene‐based high‐spin non‐Kekulé structure. Comprehensive scanning tunneling microscopy (STM) and non‐contact atomic force microscopy (nc‐AFM) evidence the structures and conformations of these unexpected products. The dynamics of the precursor bearing 9‐(2,6‐dimethylphenyl)anthracene and dihydro‐dibenzo‐cyclohepta[def]fluorene units and its reaction products on the surface are analyzed by density functional theory (DFT) and molecular dynamics (MD) simulations. Our study sheds light on the fundamental understanding of precursor design for the fabrication of π‐extended non‐benzenoid NGs on a metal surface.

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“…[16][17][18][19][20][21][22][23][24][25][26] The research in our group mainly focuses on the precision synthesis of graphene nanostructures with structurally welldefined topologies and on the exploration of their exotic electronic and magnetic properties. [16,[27][28][29][30] Among them, the chemistry of PAs has been a longstanding research interest in our group. In this review, we will highlight recent advances in the synthetic strategies and characterization methods towards π-extended PAs through both on-surface and solution-phase syntheses by our group and others.…”

Section: Introductionmentioning

confidence: 99%

“…The research in our group mainly focuses on the precision synthesis of graphene nanostructures with structurally well‐defined topologies and on the exploration of their exotic electronic and magnetic properties [16,27–30] . Among them, the chemistry of PAs has been a longstanding research interest in our group.…”

Section: Introductionmentioning

confidence: 99%

π‐Extendedperi‐Acenes: Recent Progress in Synthesis and Characterization

Ajayakumar

Feng

2022

Eur J Org Chem

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Nanographenes (NGs) with open-shell character have gained intense attention due to their potential applications in future organic nanoelectronics and spintronics. Among them, NGs bearing a pair of parallel zigzag edges, such as acenes and periacenes (PAs) bestow unique (opto)electronic and magnetic properties owing to their localized non-bonding π-state. However, their reactive zigzag edges impart intrinsic instability, leading to the challenging synthesis. The recent development of synthetic strategies provided access to several π-extended PAs, which were considered unrealistic for decades. Notably, their laterally π-extended structures of zigzag-edged graphene nanoribbons was realised via on-surface synthesis. However, synthesis of π-extended PAs in solution is still in its infancy, more intensive scientific efforts are needed to surpass the existing challenges regarding stability and solubility. This Review provides an overview of recent progress in the synthesis and characterization of PAs through a bottom-up synthetic strategy, including on-surface and solution-phase chemistry. In addition, views on existing challenges and the future prospects are also provided.

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Synthetic tuning of the quantum properties of open-shell radicaloids

Cited by 11 publications

References 82 publications

Benzo‐Extended Cyclohepta[def]fluorene Derivatives with Very Low‐Lying Triplet States

Benzo‐Extended Cyclohepta[def]fluorene Derivatives with Very Low‐Lying Triplet States

Structural Expansion of Cyclohepta[def]fluorene towards Azulene‐Embedded Non‐Benzenoid Nanographenes

π‐Extendedperi‐Acenes: Recent Progress in Synthesis and Characterization

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