Highly Stable 1,2-Dicarbonyl Radical Cations Derived from N-Heterocyclic Carbenes

Kim, Young-Suk; Byeon, Jung Eun; Jeong, Gu Yoon; Kim, Seoung Su; Song, Hayoung; Lee, Eunsung

doi:10.1021/jacs.1c00707

Cited by 34 publications

(33 citation statements)

References 67 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…NHCs featuring bulky substituents and an empty p orbital offer excellent platforms to stabilize radical species 25 – 33 . Moreover, the electronic properties of the organic radicals can be effectively tuned by varying the carbene units 34 – 36 .…”

Section: Resultsmentioning

confidence: 99%

A platform for blue-luminescent carbon-centered radicals

Wang

Chen

et al. 2022

Nat Commun

View full text Add to dashboard Cite

Organic radicals, which have unique doublet spin-configuration, provide an alternative method to overcome the efficiency limitation of organic light-emitting diodes (OLEDs) based on conventional fluorescent organic molecules. Further, they have made great breakthroughs in deep-red and near-infrared OLEDs. However, it is difficult to extend their fluorescence into a short-wavelength region because of the natural narrow bandgap of the organic radicals. Herein, we significantly expand the scope of luminescent radicals by showing a new platform of carbon-centered radicals derived from N-heterocyclic carbenes that produce blue to green emissions (444–529 nm). Time-dependent density functional theory calculations and experimental investigations disclose that the fluorescence originates from the high-energy excited states to the ground state, demonstrating an anti-Kasha behavior. The present work provides an efficient and modular approach toward a library of carbon-centered radicals that feature anti-Kasha’s rule emission, rendering them as potential new emitters in the short-wavelength region.

show abstract

Section: Resultsmentioning

confidence: 99%

A platform for blue-luminescent carbon-centered radicals

Wang

Chen

et al. 2022

Nat Commun

View full text Add to dashboard Cite

show abstract

“…Nitroxides have attracted great interest due to their numerous applications. − They have emerged as promising compounds for organic spintronics, − memory devices, − powerful organic rechargeable batteries, spin filters, , probing quantum interference effects in molecular conductance, − sophisticated artificial molecular machines that can work by consuming external energy, after the manner of motor proteins, and various new types of magnetoactive compounds saturated with organic components that could impart them with low density, elasticity, and biocompatibility. , …”

Section: Introductionmentioning

confidence: 99%

Cu(hfac)₂ Complexes with Acyclic Nitroxide Prone to Single-Crystal to Single-Crystal Transformation and Showing Mechanical Activity

Golomolzina

Толстиков

Letyagin

et al. 2022

Crystal Growth & Design

View full text Add to dashboard Cite

The heterospin solid phases of the chain polymer [Cu(hfac)2LEt]∞ and bicyclic molecule [Cu(hfac)2LEt]2-I (LR = pyrazolyl-substituted tert-butylnitroxide; 1-R-5-(tert-butyl-oxylamino)pyrazole, R = Et, Pr) were found to undergo spontaneous transformation into the bicyclic molecule [Cu(hfac)2LEt]2-II. The single-crystal to single-crystal (SC–SC) transformation of [Cu(hfac)2LEt]2-I into [Cu(hfac)2LEt]2-II was recorded by X-ray diffraction analysis of the crystal as a function of time. At 255–277 K, the [Cu(hfac)2LEt]2-I → [Cu(hfac)2LEt]2-II SC–SC transformation proceeded for 12–18 h. The [Cu(hfac)2LEt]∞ → [Cu(hfac)2LEt]2-II SC–SC phase transformation was accompanied by a change in the crystal shape, spontaneous mechanical displacements of crystals, and a change in color from orange to dark green. This process started, to a certain extent, already in the crystals lying under the layer of the mother solution. After the crystals were separated from the solution, the SC–SC transformation [Cu(hfac)2LEt]∞ → [Cu(hfac)2LEt]2-II occurred completely within 4 h at room temperature. Under normal conditions, [Cu(hfac)2LPr]2-I also undergoes transformation into [Cu(hfac)2LPr]2-II. At the macro level, the transformation [Cu(hfac)2LPr]2-I → [Cu(hfac)2LPr]2-II is accompanied by spontaneous fragmentation of crystals, visualized as a scatter of small particles of the formed phase in different directions. The reverse transformation [Cu(hfac)2LPr]2-II → [Cu(hfac)2LPr]2-I occurs when [Cu(hfac)2LPr]2-II is cooled below 225 K. When [Cu(hfac)2LPr]2-II was heated above 300 K, the irreversible SC–SC phase transformation [Cu(hfac)2LPr]2-II → [Cu(hfac)2LPr]∞ was observed, which caused a pronounced change in the color of the crystals from dark green to orange. Heat treatment of the [Cu(hfac)2LPr]∞ single crystal at 303 K on a diffractometer for 1 day or more caused partial melting of the starting crystal, disappearance of X-ray diffraction reflections from the sample under study, and appearance of reflections corresponding to the formation of the new polymer complex [Cu(hfac)2L*Pr]∞, where L*Pr is the product of transformation of the radical including the oxidation of LPr and migration of the nitroxide O atom to the heterocycle, leading to the formation of 5-(tert-butylimino)-1-propyl-1,5-dihydro-4H-pyrazol-4-one (L*Pr). The results of the X-ray diffraction study of the phase transformations completely agreed with the data of magnetochemical measurements for the complexes. Having replaced the acyclic nitroxides LEt and LPr by their diamagnetic structural analogues LPEt (2,2-dimethyl-1-(1-ethyl-1H-pyrazol-5-yl)propan-1-one) and LPPr (2,2-dimethyl-1-(1-propyl-1H-pyrazol-5-yl)propan-1-one), we obtained the complexes [Cu(hfac)2LPEt]∞, [Cu(hfac)2(LPPr)2], and [(Cu(hfac)2)3(LPPr)2], for which the transformations are absolutely not characteristic. It was also found that polymorphic transformations are also uncharacteristic of complexes of other metals with the acyclic nitroxides under study ([Zn(hfac)2LEt]2, [Zn(hfac)2LPr]...

show abstract

“…There are many reports that do not specifically mention about the bonding characteristics but consider the NHC unit as a well-defined functional unit in the organic molecules, either in the cationic state, radical or in neutral state. For example, the recently reported radical species (C, D, and E) [12][13][14][15] were considered to carry the NHC unit in its cationic state. In the N-heterocyclic olefins (NHOs) (F and G), the NHC unit is considered to carry (NHC) C umpolung character [16][17][18].…”

Section: Introductionmentioning

confidence: 99%

N‐heterocyclic carbene ligated oximes: Exploring the electronic structure and properties

Dar

Dubey

Singh

et al. 2022

Int J of Quantum Chemistry

View full text Add to dashboard Cite

Compounds with (NHC) → E coordination bond represent a family of chemical species with significant interest and their chemistry is being explored over the past 15 years, where NHC and E represent N‐heterocyclic carbene and main group elements, respectively. NHOs (N‐heterocyclic olefins) are special among these because of the (NHC) → CR2 interaction. NHOs carry nucleophilic exocyclic carbon and many interesting reactions of NHOs are due to this character. Alkylated imidazole oximes (cationic, found useful in medicinal chemistry) [(NHC) → C(H) = NOH]+ carry NHC unit as a functional group. Similarly, the corresponding nitroso‐N‐heterocyclic olefins [(NHC) → C(R)NO] also carry NHC as a functional unit. It is important to establish the interactions between the NHC unit and the rest of the molecule in these species. Density functional theory (DFT) was employed to explore the electronic structure details of a series of oximes and nitroso NHOs. The results indicate that a structure with (NHC) → C coordination interaction can be considered as one of the resonance structures of these species.

show abstract

Highly Stable 1,2-Dicarbonyl Radical Cations Derived from N-Heterocyclic Carbenes

Cited by 34 publications

References 67 publications

A platform for blue-luminescent carbon-centered radicals

A platform for blue-luminescent carbon-centered radicals

Cu(hfac)₂ Complexes with Acyclic Nitroxide Prone to Single-Crystal to Single-Crystal Transformation and Showing Mechanical Activity

N‐heterocyclic carbene ligated oximes: Exploring the electronic structure and properties

Contact Info

Product

Resources

About

Highly Stable 1,2-Dicarbonyl Radical Cations Derived from N-Heterocyclic Carbenes

Cited by 34 publications

References 67 publications

A platform for blue-luminescent carbon-centered radicals

A platform for blue-luminescent carbon-centered radicals

Cu(hfac)2 Complexes with Acyclic Nitroxide Prone to Single-Crystal to Single-Crystal Transformation and Showing Mechanical Activity

N‐heterocyclic carbene ligated oximes: Exploring the electronic structure and properties

Contact Info

Product

Resources

About

Cu(hfac)₂ Complexes with Acyclic Nitroxide Prone to Single-Crystal to Single-Crystal Transformation and Showing Mechanical Activity