Kinetics and mechanism of oxidation of <i>N</i>,<i>N</i>′-dimethyl-9,9′-biacridanyl by some π acceptors and a one-electron oxidant

Colter, Allan K.; Lai, Charles C.; Parsons, A. Gregg; Ramsey, N. Bruce; Saito, Gunzi

doi:10.1139/v85-073

Cited by 10 publications

(2 citation statements)

References 13 publications

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“…In the alternative "ET-first" mechanism the first step is an endergonic dimer-to-SC ET; subsequent rapid cleavage of the oddelectron dimer cation affords the stable monomer cation and an odd-electron monomer, the latter then undergoing an exergonic ET to another SC molecule. The "ET-first" mechanism occurs in parallel with the "cleavage-first" mechanism for many of the VII doping reactions mentioned above and is the only mechanism seen for dimeric dopants that are more strongly bound (1e 2 , as well as various organometallic dimers including [RuCp*(1,3,5-Me 3 C 6 H 3 )] 2 ) [14,46,61], as well as being observed in different contexts in, for example, the oxidation of 4 2 by various quinone derivatives [63]. For both mechanisms, the first steps are typically rate determining and thus, in general, the rate law is:…”

Section: Reactivitymentioning

confidence: 92%

Benzoimidazolium-derived dimeric and hydride n-dopants for organic electron-transport materials: impact of substitution on structures, electrochemistry, and reactivity

Mohapatra,

Al Kurdi,

Jhulki

et al. 2023

Beilstein J. Org. Chem.

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1,3-Dimethyl-2,3-dihydrobenzo[d]imidazoles, 1H, and 1,1',3,3'-tetramethyl-2,2',3,3'-tetrahydro-2,2'-bibenzo[d]imidazoles, 12, are of interest as n-dopants for organic electron-transport materials. Salts of 2-(4-(dimethylamino)phenyl)-4,7-dimethoxy-, 2-cyclohexyl-4,7-dimethoxy-, and 2-(5-(dimethylamino)thiophen-2-yl)benzo[d]imidazolium (1g–i+, respectively) have been synthesized and reduced with NaBH4 to 1gH, 1hH, and 1iH, and with Na:Hg to 1g2 and 1h2. Their electrochemistry and reactivity were compared to those derived from 2-(4-(dimethylamino)phenyl)- (1b+) and 2-cyclohexylbenzo[d]imidazolium (1e+) salts. E(1+/1•) values for 2-aryl species are less reducing than for 2-alkyl analogues, i.e., the radicals are stabilized more by aryl groups than the cations, while 4,7-dimethoxy substitution leads to more reducing E(1+/1•) values, as well as cathodic shifts in E(12•+/12) and E(1H•+/1H) values. Both the use of 3,4-dimethoxy and 2-aryl substituents accelerates the reaction of the 1H species with PC61BM. Because 2-aryl groups stabilize radicals, 1b2 and 1g2 exhibit weaker bonds than 1e2 and 1h2 and thus react with 6,13-bis(triisopropylsilylethynyl)pentacene (VII) via a “cleavage-first” pathway, while 1e2 and 1h2 react only via “electron-transfer-first”. 1h2 exhibits the most cathodic E(12•+/12) value of the dimers considered here and, therefore, reacts more rapidly than any of the other dimers with VII via “electron-transfer-first”. Crystal structures show rather long central C–C bonds for 1b2 (1.5899(11) and 1.6194(8) Å) and 1h2 (1.6299(13) Å).

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Section: Reactivitymentioning

confidence: 92%

Benzoimidazolium-derived dimeric and hydride n-dopants for organic electron-transport materials: impact of substitution on structures, electrochemistry, and reactivity

Mohapatra,

Al Kurdi,

Jhulki

et al. 2023

Beilstein J. Org. Chem.

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“…Doping of organic semiconductors by (Y-DMBI) 2 dimers [ 18 , 39 ] or by various dimers formed by 18-electron sandwich compounds [ 18 , 40 – 41 ], as well as redox reactions of other dimers formed by organic radicals [ 42 – 43 ], are known to proceed by two distinct pathways. When the dimer (D 2 ) is relatively weakly bound, its dissociation to D • can be the initial step (“cleavage-first”), which is then followed by fast electron-transfer (ET) reactions ( Scheme 2 ).…”

Section: Resultsmentioning

confidence: 99%

Beyond n-dopants for organic semiconductors: use of bibenzo[d]imidazoles in UV-promoted dehalogenation reactions of organic halides

Tang,

Brown,

Risko

et al. 2023

Beilstein J. Org. Chem.

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2,2’-Bis(4-dimethylaminophenyl)- and 2,2'-dicyclohexyl-1,1',3,3'-tetramethyl-2,2',3,3'-tetrahydro-2,2'-bibenzo[d]imidazole ((N-DMBI)2 and (Cyc-DMBI)2) are quite strong reductants with effective potentials of ca. −2 V vs ferrocenium/ferrocene, yet are relatively stable to air due to the coupling of redox and bond-breaking processes. Here, we examine their use in accomplishing electron transfer-induced bond-cleavage reactions, specifically dehalogenations. The dimers reduce halides that have reduction potentials less cathodic than ca. −2 V vs ferrocenium/ferrocene, especially under UV photoexcitation (using a 365 nm LED). In the case of benzyl halides, the products are bibenzyl derivatives, whereas aryl halides are reduced to the corresponding arenes. The potentials of the halides that can be reduced in this way, quantum-chemical calculations, and steady-state and transient absorption spectroscopy suggest that UV irradiation accelerates the reactions via cleavage of the dimers to the corresponding radical monomers.

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Bimolecular formation of radicals by hydrogen transfer, 9. Uncatalyzed transfer hydrogenation of α‐methylstyrene by 9,10‐dihydroacridine and N‐methyl‐9,10‐dihydroacridine

Friebolin

Rüchardt

1995

Liebigs Ann./Recl.

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Hydrogen is transferred from acridane (lc) and N-methylacridane (Id) to a-methyl-styrene (2) in a bimolecular uncatalyzed reaction at 260-300°C. On the basis of the activation parameters (for lc: AH* = 29.0 kcal/mol, A S 9 = -23.5 e.u. in triglyme) the kinetic isotope effect (kH/kD = 2.0, in triglyme at 3 0 0 T ) as well as the small solvent effects and from the observation of a n EPR signal of N-methylhydroacridyl radicals a three-step radical mechanism is prosposed which is initiated by a retrodisproportionation between 1 and 2. der to test if the homolytic retrodisproportionation reaction can be shifted to a true hydride transfer process by proper choice of the reactants we investigated the title reaction. Acridane (lc, X = NH) should be a much more efficient hydride donor than xanthene (1 b) or 9, lo-dihydroanthracene (la) because the acridinium ions (7c) are more effectively stabilized than the xanthylium ions (7b) or 9-hydroanthrylium ions (7a) which are formed from xanthene (lb) or DHA (la), respectively, by hydride expulsion.Scheme 2This is in contrast to current views on several similar dehydrogenationlhydrogenation reactions like quinoneL81 or nitrobenzenef91 aromatization reactions or even biochemical reductions by NADH or FADH ["]. There has been a longstanding discussion in the literature concentrating on the mechanisms of these processes, whether they are initiated by hydride transfer or electron transfer" ' 1. Initiation by a homolytic retrodisproportionation step as in Eq. (1) When a-methylstyrene (2) was heated with a 2 lofold excess of acridane (lc) to 260-300 "C in pyridine an almost quantitative yield of cumene and acridine was obtained (see Figure 1).The kinetics of the reaction followed by GC in the solvents pyridine, triglyme, p-tolunitrile, and N-methylacetamide, in which lc is sufficiently soluble (0.5-1 .O M), proved to be first order with respect to 2 and l c with standard deviations in k2 of 5 2 % and mass balances of 293% (see Table 1). When [9,9-D2]-lc, obtained from 9,10-dihydro-9-oxoacridine and LiAlD,, was used, no incorporation of deuterium into 2 was detected when 81% of the initially present 2 had reacted. This is conclusive evidence that the initiating retrodisproportionation step [analogous to step (1) in Scheme 11 is irreversible and accordingly rate-de-

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Kinetics and mechanism of oxidation of N,N′-dimethyl-9,9′-biacridanyl by some π acceptors and a one-electron oxidant

Cited by 10 publications

References 13 publications

Benzoimidazolium-derived dimeric and hydride n-dopants for organic electron-transport materials: impact of substitution on structures, electrochemistry, and reactivity

Benzoimidazolium-derived dimeric and hydride n-dopants for organic electron-transport materials: impact of substitution on structures, electrochemistry, and reactivity

Beyond n-dopants for organic semiconductors: use of bibenzo[d]imidazoles in UV-promoted dehalogenation reactions of organic halides

Bimolecular formation of radicals by hydrogen transfer, 9. Uncatalyzed transfer hydrogenation of α‐methylstyrene by 9,10‐dihydroacridine and N‐methyl‐9,10‐dihydroacridine

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