Studies of the Anodic Oxidation of 1,4-Diazabicyclo

The title compound (1) was studied at platinum and gold electrodes in acetonitrile. A reversible oxidation peak occurs at +0.30 V vs the standard potential for ferrocenium ion/ferrocene. This process is followed by a second irreversible anodic peak that is due to the oxidation of the initially formed radical cation to the dication. The principal ultimate product of the first oxidation, the conjugate acid of 1, is also oxidized over the range of potentials corresponding to the second anodic peak. The rate of disappearance of the radical cation of 1 has been determined by cyclic voltammetry. The results are best interpreted in terms of parallel pseudo-first-order decay (k(1) = 0.6 s(-)(1)) and second-order reactions. The first of these second-order reactions is either proton transfer from the radical cation to neutral 1 or hydrogen atom abstraction by the radical cation from neutral 1, reactions that give the same products (k(2) = 100 M(-)(1) s(-)(1)) and are kinetically indistinguishable. The other second-order reaction is the hydrogen-atom-transfer disproportionation of the radical cation giving the conjugate acid of 1 and the immonium ion (k(3) = 100 M(-)(1) s(-)(1)). Both second-order processes must be included to account for the results. The present results are thought to be the first experimental evidence for the occurrence of hydrogen-atom-transfer disproportionation of amine radical cations.     

去甲肾上腺素电极过程的圆二色谱电化学研究

现场圆二色薄层光谱电化学研究去甲肾上腺素的电化学氧化还原过程 .研究表明去甲肾上腺素 ( pH =7.0磷酸缓冲溶液中 )在玻碳电极上经历了不可逆的电化学氧化 ,且遵从后行化学反应 (EC)机理 ,去甲肾上腺素醌和去甲肾上腺素红的再还原遵从简单电子转移 (E)机理 .由双对数法获得去甲肾上腺素电化学氧化的式电位为E10’=0 .2 0V ,电子转移系数和电子转移数之积为αn =0 .38,标准复相电极反应常数k10 =1 .2× 1 0 -4 cm·s-1.去甲肾上腺素醌和去甲肾上腺素红的电化学还原反应参数分别为E2 0’=0 .2 5V ,αn =0 .37,k2 0 =4.4× 1 0 -5 cm·s-1和E3 0’=- 0 .2 5V ,αn =0 .33,k3 0 =1 .1× 1 0 -4 cm·s-1.     

Highly beta-selective and direct formation of 2-O-glycosylated glucosides by ring restriction into twist-boat

Three disaccharide donors, ethyl 2-O-(2,3,4-tris-O-tert-butyldimethylsilyl-beta-D-xylopyranosyl)-3,4,6-tris-O-tert-butyldimethylsilyl-1-thio-beta-D-glucopyranoside, ethyl 2-O-(2,3,4-tris-O-tert-butyldimethylsilyl-alpha-L-rhamnopyranosyl)-3,4,6-tris-O-tert-butyldimethylsilyl-1-thio-beta-D-glucopyranoside, and ethyl 2-O-(2,3,4,6-tetrakis-O-tert-butyldimethylsilyl-beta-D-glucopyranosyl)-3,4,6-tris-O-tert-butyldimethylsilyl-1-thio-beta-D-glucopyranoside, produced a highly beta-selective glycosidation up to alpha/beta = 2/98 using MeOTf as the activator and 2,6-lutidine as an additive. The ring conformations of the glucose part in these disaccharide donors were all restricted to 3S1, and the conformation would lead to the stereoselectivity.     

Supplement to the theory of normal pulse voltammetry and its application to the kinetic study of methanol oxidation on a polycrystalline platinum electrode

The theory of normal pulse voltammetry (NPV) for complex multistep multielectron transfer processes on a plane electrode was advanced and applied to the completely irreversible process of methanol oxidation to formic acid in the potential range from 0.3 to 0.8 V versus Ag/AgCl. The kinetic parameters for this process, such as the standard rate constant (k0) and anodic transfer coefficient (alpha) for this irreversible heterogeneous electron transfer process at the electrode/solution interface and apparent diffusion coefficient (D(app)) for the homogeneous charge transfer process within liquid film near the electrode surface, were obtained with NPV theory from analyzing the dependence of current-potential curves upon the sampling times. The results showed that this process is truly a very slow, completely irreversible kinetic process, as k0 is in the order of 10(-9) cm/s for the rate-determining step. The values of k0 and D(app) decreased with the increase of methanol concentration, while alpha was independent of the concentration of methanol and its value was 0.35 +/- 0.05. Theoretical fitting is very consistent with the experimental data.     

Kinetics of radical heterolysis reactions forming alkene radical cations

Rate constants for heterolytic fragmentation of beta-(ester)alkyl radicals were determined by a combination of direct laser flash photolysis studies and indirect kinetic studies. The 1,1-dimethyl-2-mesyloxyhexyl radical (4a) fragments in acetonitrile at ambient temperature with a rate constant of k(het) > 5 x 10(9) s(-1) to give the radical cation from 2-methyl-2-heptene (6), which reacts with acetonitrile with a pseudo-first-order rate constant of k = 1 x 10(6) s(-1) and is trapped by methanol in acetonitrile in a reversible reaction. The 1,1-dimethyl-2-(diphenylphosphatoxy)hexyl radical (4b) heterolyzes in acetonitrile to give radical cation 6 in an ion pair with a rate constant of k(het) = 4 x 10(6) s(-1), and the ion pair collapses with a rate constant of k < or = 1 x 10(9) s(-1). Rate constants for heterolysis of the 1,1-dimethyl-2-(2,2-diphenylcyclopropyl)-2-(diphenylphosphatoxy)ethyl radical (5a) and the 1,1-dimethyl-2-(2,2-diphenylcyclopropyl)-2-(trifluoroacetoxy)ethyl radical (5b) were measured in various solvents, and an Arrhenius function for reaction of 5a in THF was determined (log k = 11.16-5.39/2.3RT in kcal/mol). The cyclopropyl reporter group imparts a 35-fold acceleration in the rate of heterolysis of 5a in comparison to 4b. The combined results were used to generate a predictive scale for heterolysis reactions of alkyl radicals containing beta-mesyloxy, beta-diphenylphosphatoxy, and beta-trifluoroacetoxy groups as a function of solvent polarity as determined on the E(T)(30) solvent polarity scale.     

Studies of the inner reorganization energies of the cation radicals of 1,4-bis(dimethylamino)benzene, 9,10-bis(dimethylamino)anthracene, and 3,6-bis(dimethylamino)durene by photoelectron spectroscopy and reinterpretation of the mechanism of the electrochemical oxidation of the parent diamines

The inner reorganization energy of the cation radical of 1,4-bis(dimethylamino)benzene, 1, has been determined to be 0.72 +/- 0.02 eV by means of gas-phase photoelectron spectroscopy (PES). PES studies of 9,10-bis(dimethylamino)anthracene, 2, and 3,6-bis(dimethylamino)durene, 3, demonstrate that their reorganization energies are smaller than that of 1. The effect of lowering the inner reorganization energy on the rate constant for an electrochemical electron-transfer reaction is to increase the electron-transfer rate constant, k(s). However, voltammetric studies of the two-electron oxidation of 2 and 3 indicate that the values of k(s) for each step are smaller than those for 1, in contradistinction to the measured differences in reorganization energies. The voltammetric studies of 2 and 3 were reinterpreted according to a mechanism in which each step of oxidation was written as a two-step process, electron transfer with a small inner reorganization energy plus a chemical step of structural change. The agreement of simulations according to this mechanism with the experimental data was excellent. The new reaction scheme eliminated some suspicious features previously obtained with an analysis where electron transfer and structural change were considered to be concerted. In particular, all electron-transfer coefficients (alpha) were close to one-half, whereas the earlier treatment produced values of alpha much larger or smaller than one-half.     

Mechanism for radical cation transport in duplex DNA oligonucleotides

We investigated the photoinduced one-electron oxidation of a series of DNA oligomers having a covalently linked anthraquinone group (AQ) and containing [(A)(n)GG](m) or [(T)(n)GG](m) segments. These oligomers have m GG steps, where m = 4 or 6, separated by (A)(n) or (T)(n) segments, where n = 1-7 for the (A)(n) set and 1-5 for the (T)(n) set. Irradiation with UV light that is absorbed by the AQ causes injection of a radical cation into the DNA. The radical cation migrates through the DNA, causing chemical reaction, primarily at GG steps, that leads to strand cleavage after piperidine treatment. The uniform, systematic structure of the DNA oligonucleotides investigated permits the numerical solution of a kinetic scheme that models these reactions. This analysis yields two rate constants, k(hop), for hopping of the radical cation from one site to adjacent sites, and k(trap), for irreversible reaction of the radical cation with H(2)O or O(2). Analysis of these findings indicates that radical cation hopping in these duplex DNA oligomers is a process that occurs on a microsecond time scale. The value of k(hop) depends on the number of base pairs in the (A)(n) and (T)(n) segments in a systematic way. We interpret these results in terms of a thermally activated adiabatic mechanism for radical cation hopping that we identify as phonon-assisted polaron hopping.     

One-electron oxidation of 2-(4-methoxyphenyl)-2-methylpropanoic and 1-(4-methoxyphenyl)cyclopropanecarboxylic acids in aqueous solution. the involvement of radical cations and the influence of structural effects and pH on the side-chain fragmentation reactivity

A product and time-resolved kinetic study on the one-electron oxidation of 2-(4-methoxyphenyl)-2-methylpropanoic acid (2), 1-(4-methoxyphenyl)cyclopropanecarboxylic acid (3), and of the corresponding methyl esters (substrates 4 and 5, respectively) has been carried out in aqueous solution. With 2, no direct evidence for the formation of an intermediate radical cation 2*+ but only of the decarboxylated 4-methoxycumyl radical has been obtained, indicating either that 2*+ is not formed or that its decarboxylation is too fast to allow detection under the experimental conditions employed (k > 1 x 10(7) s(-1)). With 3, oxidation leads to the formation of the corresponding radical cation 3*+ or radical zwitterion -3*+ depending on pH. At pH 1.0 and 6.7, 3*+ and -3*+ have been observed to undergo decarboxylation as the exclusive side-chain fragmentation pathway with rate constants k = 4.6 x 10(3) and 2.3 x 10(4) s(-1), respectively. With methyl esters 4 and 5, direct evidence for the formation of the corresponding radical cations 4*+ and 5*+ has been obtained. Both radical cations have been observed to display a very low reactivity and an upper limit for their decay rate constants has been determined as k < 10(3) s(-1). Comparison between the one-electron oxidation reactions of 2 and 3 shows that the replacement of the C(CH3)2 moiety with a cyclopropyl group determines a decrease in decarboxylation rate constant of more than 3 orders of magnitude. This large difference in reactivity has been qualitatively explained in terms of three main contributions: substrate oxidation potential, stability of the carbon-centered radical formed after decarboxylation, and stereoelectronic effects. In basic solution, -3*+ and 5*+ have been observed to react with -OH in a process that is assigned to the -OH-induced ring-opening of the cyclopropane ring, and the corresponding second-order rate constants (k-OH) have been obtained. With -3*+, competition between decarboxylation and -OH-induced cyclopropane ring-opening is observed at pH >or=10, with the latter process that becomes the major fragmentation pathway around pH 12.     

Transients in the oxidative and H-atom-induced degradation of 1,3,5-trithiane. Time-resolved studies in aqueous solution

The (*)OH-induced oxidation of 1,3,5-trithiacyclohexane (1) in aqueous solution was studied by means of pulse radiolysis with optical and conductivity detection. This oxidation leads, via a short-lived (*)OH radical adduct (<1 micros), to the radical cation 1(*+) showing a broad absorption with lambda(max) equal to 610 nm. A defined pathway of the decay of 1(*+) is proton elimination. It occurs with k = (2.2 +/- 0.2) x 10(4) s(-1) and yields the cyclic C-centered radical 1(-H)(*). The latter radical decays via ring opening (beta-scission) with an estimated rate constant of about 10(5) s(-1). A distinct, immediate product (formed with the same rate constant) is characterized by a narrow absorption band with lambda(max) = 310 nm and is attributed to the presence of a dithioester function. The formation of the 310 nm absorption can be suppressed in the presence of oxygen, the rationale for this being a reaction of the C-centered cyclic radical 1(-H)(*) with O(2). The disappearance of the 310 nm band (with a rate constant of 900 s(-1)) is associated with the hydrolysis of the dithioester functionality. A further aspect of this study deals with the reaction of H(*) atoms with 1 which yields a strongly absorbing, three-electron-bonded 2sigma/1sigma* radical cation [1(S therefore S)-H](+) (lambda(max) = 400 nm). Its formation is based on an addition of H(*) to one of the sulfur atoms, followed by beta-scission, intramolecular sulfur-sulfur coupling (constituting a ring contraction), and further stabilization of the S therefore S bond thus formed by protonation. [1(S therefore S)-H](+) decays with a first-order rate constant of about 10(4) s(-1). Its formation can be suppressed by the addition of oxygen which scavenges the H(*) atoms prior to their reaction with 1. Complementary time-resolved conductivity experiments have provided information on the quantification of the 1(*+) radical cation yield, the cationic longer-lived follow-up species, extinction coefficients, and kinetics concerning deprotonation processes as well as further reaction steps after hydrolysis of the transient dithioesters. The results are also discussed in the light of previous photochemical studies.     

Electrochemical study of methylcobalamin Determination of the reduction potential for a quasireversible system with a fast following reaction

The reductive electrochemistry of methylocobalamin in nonaqueous solution is typical of many electrochemical mechanisms in that the initial electron transfer at the electrode is followed by a fast chemical reaction. The rate constant of the following chemical step, methyl radical cleavage, was measured by double potential step chronoamperometry to be 590 sec(-1) in a solvent mixture (DMF 40%, methanol 60%, at -30 degrees ). The cyclic voltammetric response in the slow scan-rate regime was analyzed by the simulation-fitting program CVFIT to extract the remaining parameters of the electrode reaction-chemical reaction mechanism: the formal reduction potential (E(0') = -1.529 +/- 0.004 V), the standard heterogeneous rate-constant (k(0) = 0.012 +/- 0.002 cm/sec), and the transfer coefficient (alpha = 0.78 +/- 0.02). This method of analysis allows for the rigorous determination of reduction potentials under conditions where the cyclic voltammetric response appears irreversible (no reverse peak is observed). A detailed analysis of the actual reversibility of the system and its effect on the apparent transfer coefficient is presented.     

Voltammetric and electrochemical ESR studies of oxidation reactions mediated by tris(4-bromophenyl)amine in acetonitrile

The electrochemical oxidation of tris(4-bromophenyl)amine in the presence of 2,6-lutidine is examined in acetonitrile. Voltammetric and spectroscopic investigations suggest that the electrogenerated triaryl aminium radical cation oxidizes 2,6-lutidine in an EC' mechanism, and an equilibrium constant for this homogeneous electron transfer is estimated. The mediated oxidation of a protected phenyl selenoglycoside by this reaction mixture is studied by the use of electrochemical ESR, employing a tubular flow cell, and signal intensity data is found to be consistent with the proposed mechanism, allowing the determination of kinetic parameters by computational simulation. Products of the mediated glycoside oxidation are determined by proton NMR and mass spectrometry.     

Spectroelectrochemical characterization of Si-bridged diphenylamines: influence of Si-bridging upon electronic structures of diphenylamines.

Spectroelectrochemical properties of monosilane bridged diphenylamine (5,10-dihydro-2,8-diphenyl-5, 10,10-trimethylphenazasiline, Phenaz) and disilane bridged diphenylamine (2,8-diphenyl-10,11-dihydro-10,11-disila-5,10,10,11,11-pentamethyldibenzo[b,f]azepine, DSiAzep) were investigated. The electrochemical oxidation of Phenaz was reversible and its cyclic voltammogram was almost the same shape as that of diphenylamine (DPA). The electrochemical oxidation of DSiAzep was followed by irreversible reactions leading to the cleavage of the Si-Si bond. On electrochemical oxidations of Phenaz and DPA, the formation of a stable radical cation was observed with UV-Vis spectroscopy. In comparison with the absorption characteristics of oxidized radical cations, it was seen that the oxidized radical cation of Phenaz was more delocalized than that of DPA. In the same way, absorption characteristics of oxidized DSiAzep were observed to be different from those observed in Phenaz and DPA.     

The first calibration of an aminiumyl radical ion clock: why N-cyclopropylanilines may be poor mechanistic probes for single electron transfer

Using direct and indirect electrochemical methods, the rate constant for ring opening of the radical cation generated from N-cyclopropyl-N-methylaniline was found to be 4.1 x 10(4) s(-1).     

Electroreduction of a series of alkylcobalamins: mechanism of stepwise reductive cleavage of the Co-C bond

The electrochemical (EC) reduction mechanism of methylcobalamin (Me-Cbl) in a mixed DMF/MeOH solvent in 0.2 M tetrabutylammonium fluoroborate electrolyte was studied as a function of temperature and solvent ratio vs a nonaqueous Ag/AgCl/Cl(-) reference electrode. Double-potential-step chronoamperometry allowed the rate constant of the subsequent homogeneous reaction to be measured over the temperature range from 0 to -80 degrees C in 40:60 and 50:50 DMF:MeOH ratios. Activation enthalpies are 5.8 +/- 0.5 and 7.6 +/- 0.3 kcal/mol in the 40:60 and 50:50 mixtures of DMF/MeOH, respectively. Digital simulation and curve-fitting for an EC mechanism using a predetermined homogeneous rate constant of 5.5 x 10(3) s(-1) give E degrees' = -1.466 V, k degrees = 0.016 cm/s, and alpha = 0.77 at 20 degrees C for a quasi-reversible electrode process. Digital simulation of the results of Lexa and Savéant (J. Am. Chem. Soc. 1978, 100, 3220-3222) shows that the mechanism is a series of stepwise homogeneous equilibrium processes with an irreversible step following the initial electron transfer (ET) and allows estimation of the equilibrium and rate constants of these reactions. An electron coupling matrix element of H(kA) = (4.7 +/- 1.1) x 10(-4) eV ( approximately 46 J/mol) is calculated for the nonadiabatic ET step for reduction to the radical anion. A reversible bond dissociation enthalpy for homolytic cleavage of Me-Cbl is calculated as 31 +/- 2 kcal/mol. The voltammetry of the ethyl-, n-propyl-, n-butyl-, isobutyl-, and adenosyl-substituted cobalamin was studied, and estimated reversible redox potentials were correlated with Co-C bond distances as determined by DFT (B3LYP/ LANL2DZ) calculations.     

乙酰胆碱酯酶催化水解产物的电化学行为

报道了乙酰硫代胆碱水解产物硫代胆碱在玻碳电极上的电化学行为。以乙酰硫代胆碱作底物,在一定条件下乙酰胆碱酯酶催化底物水解,生成电活性物质硫代胆碱。利用循环伏安法和线性扫描伏安法研究了酶催化水解产物硫代胆碱在玻碳电极上的电化学行为。结果表明:在0.1mol/L的B-R缓冲溶液(pH7.0)中,硫代胆碱有一灵敏的氧化峰,峰电位EP=0.32V(vs.SCE);该体系属具有吸附性的不可逆过程。实验测得电子转移数为2,电极反应速率常数k=0.29s-1。     

Kinetic Studies of Electrochemical Oxidation of 1,3-Benzenedithiol

The electrochemical oxidation of 1, 3-benzenedithiol was investigated in a 0. 100 mol/L tetrabutylammonium perchlorate/acetonitrile electrolyte. The electrochemical techniques used were potential sweep, bulk electrolysis, rotating disc and the potential step method. The combination of the techniques yielded the number of electrons transferred per molecule, the reaction order, the transfer coefficient, the diffusion coefficient and concentration of dithiol anions, the standard heterogeneous rate constant as well as the formal potential and equilibrium constant of the preceeding dissociation reaction. This paper also illustrates the methods for studying the electrode kinetics of reactions which (a) involve a chemical reaction preceeding the electron-transfer process, (b) have insoluble polymer products, and (c) are totally irreversible.     

A multiswitchable poly(terthiophene) bearing a spiropyran functionality: understanding photo- and electrochemical control

An electroactive nitrospiropyran-substituted polyterthiophene, poly(2-(3,3'-dimethylindoline-6'-nitrobenzospiropyranyl)ethyl 4,4'-didecyloxy-2,2':5',2'-terthiophene-3'-acetate), has been synthesized for the first time. The spiropyran, incorporated into the polymer backbone by covalent attachment to the alkoxyterthiophene monomer units, leads to multiple colored states as a result of both photochemical and electrochemical isomerization of the spiropyran moiety to merocyanine forms as well as electrochemical oxidation of the polyterthiophene backbone and the merocyanine substituents. While electrochemical polymerization of the terthiophene monomer can take place without oxidation of the spiropyran, increasing the oxidation potential leads to complex electrochemistry that clearly involves this substituent. To understand this complex behavior, the first detailed electrochemical study of the oxidation of the precursor spiropyran, 1-(2-hydroxyethyl)-3,3-dimethylindoline-6'-nitrobenzospiropyran, was undertaken, showing that, in solution, an irreversible electrochemical oxidation of the spiropyran occurs leading to reversible redox behavior of at least two merocyanine isomers. With these insights, an extensive electrochemical and spectroelectrochemical study of the nitrospiropyran-substituted polyterthiophene films reveals an initial irreversible electrochemical oxidative ring-opening of the spiropyran to oxidized merocyanine. Subsequent reduction and cyclic voltammetry of the resulting nitromerocyanine-substituted polyterthiophene film gives rise to the formation of both merocyanine π-dimers or oligomers and π-radical cation dimers, between polymer chains. Although merocyanine formation is not electrochemically reversible, the spiropyran can be photochemically regenerated, through irradiation with visible light. Subsequent electrochemical oxidation of the nitrospiropyran-substituted polymer reduces the efficiency of the spiropyran to merocyanine isomerization, providing electrochemical control over the polymer properties. SEM and AFM images support the conclusion that the bulky spiropyran substituent is electrochemically isomerized to the planar merocyanine moiety, affording a smoother polymer film. The conductivity of the freestanding polymer film was found to be 0.4 S cm(-1).     

Scavenging of acetylperoxyl radicals and quenching of triplet diacetyl by beta-carotene: mechanisms and kinetics

Beta-carotene scavenges triplet diacetyl generated by laser flash photolysis with a second-order rate constant of 9.1+/-0.9 x 10(9) M(-1) s(-1) in deaerated benzene at 20 degrees C. In the presence of oxygen diacetyl dissociates to generate acetylperoxyl radicals. It is demonstrated that diacetyl does not dissociate to any appreciable extent in the absence of oxygen. The acetylperoxyl radical is scavenged by beta-carotene with second-order rate constant 9.2+/-0.6 x 10(8) M(-1) s(-1) in aerated benzene at 20 degrees C to give an adduct between the acetylperoxyl radical and beta-carotene, whereas no evidence of oxidation of beta-carotene by the strongly oxidizing acetylperoxyl radical to give the beta-carotene radical cation is found. This adduct decays with first-order rate constant 1.35+/-0.16 x 10(3) s(-1) to give (presumably) a beta-carotene epoxide and the acetyloxyl radical.     

Reaction of SO4˙⁻ with an oligomer of poly(sodium styrene sulfonate). Probing the mechanism of damage to fuel cell membranes

Clarification of the mechanism of degradation of model compounds for polymers used in polymer electrolyte fuel cells may identify intermediates that propagate damage; such knowledge can be used to improve the lifetime of fuel cell membranes, a central issue to continued progress in fuel cell technology. In proton-exchange membranes based on poly(styrene sulfonic acid), hydroxycyclohexadienyl radicals are formed after reaction with HO˙ and thought to decay to short-lived radical cations at low pH. To clarify subsequent reactions, we generated radical cations by reaction of SO(4)˙(-) with oligomers of poly(styrene sulfonic acid) (MW ≈ 1100 Da). At 295 K, this reaction proceeds with k = (4.5 ± 0.6) × 10(8) M(-1) s(-1), both at pH 2.4 and 3.4, and yields benzyl radicals with an estimated yield of ≤60% relative to [SO(4)˙(-)]. The radical cation is too short-lived to be observed: based on a benzyl radical yield of 60%, a lower limit of k > 6.8 × 10(5) s(-1) for the intramolecular transformation of the aromatic radical cation of the oligomer to a benzyl radical is deduced. Our results show that formation of the benzyl radical, an important precursor in the breakdown of the polymer, is irreversible.     

Highly conjugated p-quinonoid pi-extended tetrathiafulvalene derivatives: a class of highly distorted electron donors

A new class of pi-extended TTF-type electron donors (11 a-c) has been synthesized by Wittig-Horner olefination of bianthrone (9) with 1,3-dithiole phosphonate esters (10 a-c). In cyclic voltammetry experiments, donors 11 a-c reveal a single, electrochemically irreversible oxidation-yielding the corresponding dicationic products-at relatively low oxidation potentials (approximately 0.7-0.8 V). Theoretical calculations, performed at the DFT level (B3 P86/6-31 G*), predict a highly-folded C(2h) structure for 11 a. In the ground state, the molecule adopts a double saddle-like conformation to compensate the steric hindrance. The calculations suggest that the intramolecular charge transfer associated with the HOMO-->LUMO transition is responsible for an absorption band observed above 400 nm. While the radical cation 11 a*+ retains the folded C(2h) structure predicted for the neutral molecule as the most stable conformation, the dication 11 a(2+) has a fully aromatic D(2) structure, formed by an orthogonal 9,9'-bianthryl central unit to which two singly-charged dithiole rings are attached. The drastic conformational changes that compounds 11 undergo upon oxidation account for their electrochemical properties. By means of pulse radiolysis measurements, radical-induced one-electron oxidation of 11 a-c was shown to lead to the radical cation species (11 a-c*+), which were found to disproportionate with generation of the respective dication species (11 a-c(2+)) and the neutral molecules (11 a-c).