Stable free radicals. 12. New aspects of the behavior of 1-alkyl-4-(carboalkoxy)- and 1-alkyl-4-carbamidopyridinyl radicals in solution and in thin films

Hermolin, J.; Levin, M.; Kosower, Edward M.

doi:10.1021/ja00406a023

Cited by 36 publications

(18 citation statements)

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“…The absence of the reverse oxidation wave or its large separation from the reduction peaks and dependence of the reduction potential on the scan rate confirmed the irreversibility of the electrochemical reduction of 1 – 5 and 1a – 3a (Figure C) . This is consistent with the irreversibility of N -methylpyridinium and bis(pyridinium)alkanes reduction leading to 4,4′-coupled σ-dimers and cyclomers, correspondingly (Figure , A). − Interestingly, irreversibility is not affected by CB[7], suggesting that cyclomerization and/or σ-dimerization is not prevented by inclusion within CB[7]. This is likely the result of neutral diradical intermediates, generated upon two-electron reduction, exiting the CB[7] host.…”

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confidence: 67%

Modulation of Reduction Potentials of Bis(pyridinium)alkane Dications through Encapsulation within Cucurbit[7]uril

et al. 2019

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Supramolecular modulation of reduction potentials of two series of bis(pyridinium)alkane salts is described. Study of the encapsulation of bis(pyridinium)alkane guests within the CB[7] cavity revealed the critical influence of the linker length and the position of the heteroatom on the reduction potentials of encapsulated guests. CB[7] complexation of pyridinium salts induced reduction potential changes ranging between +50 and −430 mV. Noncovalent modulation of the electron-accepting ability of organic cations can be utilized in electron-transfer-initiated reactions.

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confidence: 67%

Modulation of Reduction Potentials of Bis(pyridinium)alkane Dications through Encapsulation within Cucurbit[7]uril

et al. 2019

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“…At low sweep rates, the first reduction step of 6O + and most acridine-based models (Ph-Acr + , Me 2 N-Acr + , 4O + , 2O + , and 3N + ) exhibited reversible electrochemical behavior, indicating good chemical stability of the corresponding radicals. On the other hand, the first reduction potentials of pyridinium (CN-BNA + , HE + , BNA + and Me-MNA + ) and imidazolium (BIM + and CAF + ) models appear at more negative potentials and are chemically irreversible, possibly due to radical dimerization. − The stability of pyridine-based radicals can be increased by the introduction of substituents in the 4-position . The lower reactivity of acridine-based radicals over the pyridine-based structures is likely due to higher delocalization of the unpaired spin in the acridine-based radicals .…”

Section: Results and Discussionmentioning

confidence: 99%

Thermodynamic Hydricities of Biomimetic Organic Hydride Donors

et al. 2018

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Thermodynamic hydricities (Δ G) in acetonitrile and dimethyl sulfoxide have been calculated and experimentally measured for several metal-free hydride donors: NADH analogs (BNAH, CN-BNAH, Me-MNAH, HEH), methylene tetrahydromethanopterin analogs (BIMH, CAFH), acridine derivatives (Ph-AcrH, MeN-AcrH, T-AcrH, 4OH, 2OH, 3NH), and a triarylmethane derivative (6OH). The calculated hydricity values, obtained using density functional theory, showed a reasonably good match (within 3 kcal/mol) with the experimental values, obtained using "potential p K" and "hydride-transfer" methods. The hydride donor abilities of model compounds were in the 48.7-85.8 kcal/mol (acetonitrile) and 46.9-84.1 kcal/mol (DMSO) range, making them comparable to previously studied first-row transition metal hydride complexes. To evaluate the relevance of entropic contribution to the overall hydricity, Gibbs free energy differences (Δ G) obtained in this work were compared with the enthalpy (Δ H) values obtained by others. The results indicate that, even though Δ H values exhibit the same trends as Δ G, the differences between room-temperature Δ G and Δ H values range from 3 to 9 kcal/mol. This study also reports a new metal-free hydride donor, namely, an acridine-based compound 3NH, whose hydricity exceeds that of NaBH. Collectively, this work gives a perspective of use metal-free hydride catalysts in fuel-forming and other reduction processes.

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“…It is dominated by two absorption bands, one at ≈ 400 nm, and a lower‐intensity broad absorption band at ≈ 750 nm. The high‐energy absorption band is characteristic of the pyridinyl radical and matches well with the reported spectrum of the 4‐methoxycarbonyl‐ N ‐methylpyridinyl radical 16. The mechanism for the photoinduced reaction is proposed in Scheme 5.…”

Section: Resultsmentioning

confidence: 99%

Luminescent Molecular Copper(I) Alkynyl Open Cubes: Synthesis, Structural Characterization, Electronic Structure, Photophysics, and Photochemistry

Chan

Cheung

Lam

et al. 2006

Chemistry An Asian Journal

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A novel class of tetranuclear copper(I) alkynyl complexes with an "open-cube" structure was synthesized. The crystal structure of [Cu4{P(p-MeC6H4)3}4(mu3-eta(1),eta(1),eta(2)-C[triple bond]C-p-MeOC6H4)3]PF6 was determined. These complexes were found to display dual emission behavior. Through systematic comparison studies on the electronic absorption and photoluminescence properties of a series of [Cu4(PR3)4(mu3-eta(1),eta(1),eta(2)-C[triple bond]CR')3]+ complexes, together with density functional theory (DFT) calculations at the PBE1PBE level on the model complex [Cu4(PH3)4(mu3-eta(1),eta(1),eta(2)-C[triple bond]C-p-MeOC6H4)3]+, the nature of their emission origins was probed. Their photochemical properties were also investigated by oxidative quenching experiments and transient absorption spectroscopy.

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Stable free radicals. 12. New aspects of the behavior of 1-alkyl-4-(carboalkoxy)- and 1-alkyl-4-carbamidopyridinyl radicals in solution and in thin films

Cited by 36 publications

References 0 publications

Modulation of Reduction Potentials of Bis(pyridinium)alkane Dications through Encapsulation within Cucurbit[7]uril

Modulation of Reduction Potentials of Bis(pyridinium)alkane Dications through Encapsulation within Cucurbit[7]uril

Thermodynamic Hydricities of Biomimetic Organic Hydride Donors

Luminescent Molecular Copper(I) Alkynyl Open Cubes: Synthesis, Structural Characterization, Electronic Structure, Photophysics, and Photochemistry

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