Carbene derived diradicaloids – building blocks for singlet fission?

Messelberger, Julian; Grünwald, Annette; Pinter, Piermaria; Hansmann, Max M.; Munz, Dominik

doi:10.1039/c8sc01999a

Cited by 72 publications

(60 citation statements)

References 168 publications

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“…This vertical Δ E S‐T value of VI is close to the results of multi‐reference second‐order n ‐electron valence state perturbation theory (NEVPT2) method by Munz et al. (−41.0 kcal mol −1 , for details see the Supporting Information) . It is important to note that this tendency was found to hold when we estimated the Δ E S‐T values at the UB3LYP/6–311G* level using the approximate spin‐projection scheme .…”

Section: Figuresupporting

confidence: 86%

Diradical Character Enhancement by Spacing: N‐Heterocyclic Carbene Analogues of Müller's Hydrocarbon

Rottschäfer

Busch

Neumann

et al. 2018

Chemistry A European J

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Two-fold C-C cross-coupling of N-heterocyclic carbenes [NHCs; SIPr=C(NArCH ) , 1; IPr=C(NArCH) , 2; Me-IPr=C(NArCMe) , 3; Ar=2,6-iPr C H ] with 4,4''-diiodo-p-terphenyl under Ni catalysis furnished [(SIPr)(C H ) (SIPr)](I) (4), [(IPr)(C H ) (IPr)](I) (5), and [(Me-IPr)(C H ) (Me-IPr)](I) (6). Two-electron reduction of 4-6 with KC readily afforded NHC analogues of Müller's hydrocarbon (MH), [(SIPr)(C H ) (SIPr)] (7), [(IPr)(C H ) (IPr)] (8), and [(Me-IPr)(C H ) (Me-IPr)] (9), respectively, as highly colored crystalline solids. Quantum chemical calculations suggested that the singlet ground state for 7-9 possesses a vertical singlet-triplet energy gap ΔE of -7.24 to -7.60 kcal mol , which is significantly lower compared to that of the NHC analogues of Thiele's (TH) and Chichibabin's (CH) (18-38 kcal mol ) hydrocarbons. Importantly, the calculated diradical character (y) of 7-9 (y≈0.6) is considerably higher compared to that of the related TH and CH (y=0.1-0.4), suggesting the open-shell singlet character of 7-9.

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Section: Figuresupporting

confidence: 86%

Diradical Character Enhancement by Spacing: N‐Heterocyclic Carbene Analogues of Müller's Hydrocarbon

Rottschäfer

Busch

Neumann

et al. 2018

Chemistry A European J

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“…14 Paralleling the rich chemistry of TTF derivatives, subsequent studies were directed at introducing bridges in order to obtain mixed-valent compounds and singlet biradicaloids. [38][39][40][41] Other investigations explored complementary synthetic approaches [42][43][44][45] or focused on other heterocycles as building blocks. [46][47][48] In combination with further related reports, [49][50][51][52] a considerable variety of such two-stage redox systems are now available.…”

Section: Introductionmentioning

confidence: 99%

Aromaticity and sterics control whether a cationic olefin radical is resistant to disproportionation

et al. 2020

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“…Further, it gives the coefficient of the configuration interaction (CI) vector, 0.99 for the closed‐shell 2,0 configuration, 0.0 for the 1,1 configuration, and 0.01 for the 0,2 configuration. Neese's diradicaloid index is found to be 2% …”

Section: Resultsmentioning

confidence: 97%

“…Neese's diradicaloid index is found to be 2%. [30,31] 3.2 | CMO-NICS analysis NICS values are calculated by placing ghost atoms (BQs) at the center of the ring and 1 Å above the ring. The corresponding values of NICS(0), NICS(0)zz, NICS(1), and NICS(1)zz are presented in Table 2.…”

Section: Correlation Of the Experimental Nmr Results With Structurementioning

confidence: 99%

Aromaticity of N‐heterocyclic carbene and its analogues: Magnetically induced ring current perspective

Patra

Mandal

2019

Int J of Quantum Chemistry

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The N‐heterocyclic carbene, imidazole‐2‐ylidene, and its main group (13‐15) analogues contain cyclically conjugated 6π electrons. Experimental 1H nuclear magnetic resonance (NMR) spectra suggest an increase in aromaticity along a period from left to right. Whereas the order along a group is as follows: period 2 > period 5 > period 4 > period 3 due to change in structure. To understand the order of aromaticity, the magnetically induced ring currents of the molecules are calculated using aromatic ring current shielding, gauge‐including magnetically induced currents (GIMIC) method and Stanger's σ‐model applying the gauge‐including atomic orbitals NMR technique. It is found that GIMIC best describes the order of aromaticity especially along a group where current‐profile changes on the bivalent atom down a group due to change in electron density. Moreover, the GIMIC provides the visualization of current by sign modulus and the anisotropy of the induced current density plots.

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Carbene derived diradicaloids – building blocks for singlet fission?

Abstract: Carbene–bridge–carbene ensembles: tunable diradicaloids for singlet fission?

Cited by 72 publications

References 168 publications

Diradical Character Enhancement by Spacing: N‐Heterocyclic Carbene Analogues of Müller's Hydrocarbon

Diradical Character Enhancement by Spacing: N‐Heterocyclic Carbene Analogues of Müller's Hydrocarbon

Aromaticity and sterics control whether a cationic olefin radical is resistant to disproportionation

Aromaticity of N‐heterocyclic carbene and its analogues: Magnetically induced ring current perspective

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