Synthesis and Properties of Quinoidal Fluorenofluorenes

Barker, Joshua E.; Frederickson, Conerd K.; Jones, Michael H.; Zakharov, Lev N.; Haley, Michael M.

doi:10.1021/acs.orglett.7b02605

Cited by 47 publications

(46 citation statements)

References 36 publications

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“…Recently, aided by the disclosure of a key bistriflate intermediate by the McCulloch group, [ 32 ] graduate student Josh Barker recently returned to the FF arena and successfully prepared the linearly fused, π‐expanded [1,2‐ b ]IF analogue, fluoreno[3,2‐ b ]fluorene 8. [ 33 ] Despite the different mode of fusion of the indene units to the central naphthalene, this work led to the same conclusions experimentally and computationally as the [4,3‐ c ]FF study, more specifically, the observed structural and optical properties of [3,2‐ b ]FF 8 were consistent with a quinoidal core, that is, a closed‐shell molecule. Given that the changes to molecule properties were relatively modest for 8 and 10 , we were curious whether further expansion to an anthracene as the core motif would have a greater effect on the overall properties.…”

Section: First Steps At π‐Expansionsupporting

confidence: 64%

Learning how to fine‐tune diradical properties by structure refinement

Dressler

Haley

2020

J of Physical Organic Chem

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The literature has seen a large increase in the number of new carbon-based organic diradicals/diradicaloids in recent years. While a plethora of new and exciting structures have been created, there seemingly is a gap in knowledge of what fundamental electronic parameters are in play and thus how to rationally manipulate said parameters to "fine tune" the resultant diradical properties. Since 2014, the Haley group has been exploring methods to systematically alter the diradical character and the singlet-triplet energy gap in said class of molecules. Our entrance into organic diradicals began with the π-expansion of the benzene core of indeno[1,2-b]fluorene up to the anthracene core of diindenoanthracene (DIAn). DIAn possessed moderate diradical character (y = 0.62) with a surprising level of stability (more than 2 months in solution). From this molecular blueprint for producing stable diradicals, the Haley lab has investigated how to fine tune diradical properties via structural changes in two key positions: (a) the length of the acene core and (b) thoughtful exchange of the outer arenes. With this strategy at our disposal, we can make large scale changes to the diradical character index and singlet-triplet energy gap through changing the core length, and these properties can be further fine-tuned in a series of closely related diradicals by careful exchange of the outer arenes utilizing the straightforward methods described in this mini-review.

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Section: First Steps At π‐Expansionsupporting

confidence: 64%

Learning how to fine‐tune diradical properties by structure refinement

Dressler

Haley

2020

J of Physical Organic Chem

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“…Among them, indeno[2,1‐ b ]fluorene ( I , Figure ) and indeno[1,2‐ a ]fluorene ( III ) have open‐shell singlet and triplet ground states, respectively. Further extending the central PHs from benzene to naphthalene ( II and IV ), anthracene ( V ), perylene ( IX ), or pyrene ( X and XI ), gives rise to either closed‐shell or open‐shell singlet ground states with different electron exchange interaction and diradical characters, depending on the fusion patterns and the structures of central PHs (Figure ). So far, however, most diindeno‐fused PHs are derived from planar skeletons.…”

Section: Figuresupporting

confidence: 54%

Stable Diindeno‐Fused Corannulene Regioisomers with Open‐Shell Singlet Ground States and Large Diradical Characters

Liu

et al. 2019

Angewandte Chemie

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The synthesis of open‐shell polycyclic hydrocarbons with large diradical characters is challenging because of their high reactivities. Herein, two diindeno‐fused corannulene regioisomers DIC‐1 and DIC‐2, curved fragments of fullerene C104, were synthesized that exhibit open‐shell singlet ground states. The incorporation of the curved and non‐alternant corannulene moiety within diradical systems leads to significant diradical characters as high as 0.98 for DIC‐1 and 0.89 for DIC‐2. Such high diradical characters can presumably be ascribed to the re‐aromatization of the corannulene π system. Although the DIC compounds have large diradical characters, they display excellent stability under ambient conditions. The half‐lives are 37 days for DIC‐1 and 6.6 days for DIC‐2 in solution. This work offers a new design strategy towards diradicaloids with large diradical characters yet maintain high stability.

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“…3 represents the family of stabilized diindenoarene biradicaloids, [7][8][9] which comprises indenouorenes [10][11][12][13][14] and their larger congeners, e.g. ones containing naphthalene, [15][16][17][18] pyrene, 19 perylene, 20 and bischrysene 21 cores, or extended by benzenoid fusion. 9,[22][23][24] Here we show that by a judicious yet simple modication of the classical structure of Chichibabin's hydrocarbon 1, it is possible to create a much more stable biradicaloid system.…”

Section: Introductionmentioning

confidence: 99%