2009
DOI: 10.1021/jo8019829
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Structure−Property Relationships of Stable Free Radicals: Verdazyls with Electron-Rich Aryl Substituents

Abstract: Substitution of the 3 position of 6-oxoverdazyl free radicals with electron-rich arylamines, phenols, and aryl ethers elicits changes in the UV-vis spectra and in the pK(a) of the aryl substituents consistent with the verdazyl being electron withdrawing. The pK(a) of substituents is decreased: in 80% methanol phenols 3a and 3b have pK(a) of 10.4 and 10.9, respectively, while the ammonium ion from protonation of 3j has pK(a) = 2.4. On the basis of these measurements, Hammett parameters for the verdazyl have bee… Show more

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Cited by 41 publications
(59 citation statements)
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“…The fact that the transition energy of the o-OMe structure is the largest and differs significantly from the corresponding hydroxyl case is related to the torsion between the two rings that is negligible for all compounds of Table III but for o-OMe. For this latter verdazyl, we calculate a dihedral angle of 52 degrees between the two moieties, in good agreement with the XRD measure (60 degrees) [37].…”
Section: Chemistruck Chambers and Brook Have Proposed A Series Of Stsupporting
confidence: 75%
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“…The fact that the transition energy of the o-OMe structure is the largest and differs significantly from the corresponding hydroxyl case is related to the torsion between the two rings that is negligible for all compounds of Table III but for o-OMe. For this latter verdazyl, we calculate a dihedral angle of 52 degrees between the two moieties, in good agreement with the XRD measure (60 degrees) [37].…”
Section: Chemistruck Chambers and Brook Have Proposed A Series Of Stsupporting
confidence: 75%
“…For the mono-anion of the p-hydroxyl derivative, Chemistruck and coworkers observe a significant bathochromic shift compared to the neutral form [37], and TD-PBE0 delivers the same trend. However, the λ max of the anion is experimentally close to 2.15 eV in acetonitrile (from Fig.…”
Section: Chemistruck Chambers and Brook Have Proposed A Series Of Stmentioning
confidence: 90%
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“…42,47 For both of these verdazyl types the C3 substituent has a significant influence on the absorption wavelength: radicals with R = hydrogen or alkyl generally have λ max values about 50 nm lower than the corresponding species with a C3 phenyl group. Electron donating groups on the C3 phenyl cause further red shifts, 55 suggesting that the lowest energy absorption involves a transition from an occupied orbital to the singly occupied molecular orbital (SOMO). The substituents on the nitrogen atoms are also important: 6-oxoverdazyls with N-alkyl groups (e.g., R , R = methyl, isopropyl) have absorption bands near 400-450 nm and appear yellow to dark orange, whereas N-aryl substituted 6-oxoverdazyls are deep red with λ max ranging from 500 to 550 nm.…”
Section: Verdazyls From Hydrazides and Bis-hydrazides: 6-oxoverdazylsmentioning
confidence: 99%