4217-54-3Relevant articles and documents
Efficient Six-Electron Photoreduction of Nitrobenzene Derivatives by 10-Methyl-9,10-dihydroacridine in the Presence of Perchloric Acid
Fukuzumi, Shunichi,Tokuda, Yoshihiro
, p. 831 - 836 (1992)
Photoreduction of nitrobenzene derivatives by 10-methyl-9,10-dihydroacridine (AcrH2) occurs efficiently in the presence of perchloric acid in acetonitrile containing H2O (0.50 mol dm-3) to yield the corresponding six-electron reduced products (aniline derivatives) and 10-methylacridinium ion efficiently.The initial two-electron reduction of PhNO2 to PhNO by AcrH2 in the six-electron reduction of nitrobenzene (PhNO2) is started by electron transfer from AcrH2 to the n,?* triplet state (3PhNO2*), followed by acid-catalyzed thermal reduction of PhNO to PhNHOH by AcrH2 and the subsequent photoreduction of PhNHOH to PhNH2 by AcrH2.
Oxygen-initiated chain mechanism for hydride transfer between NADH and NAD+ models. Reaction of 1-benzyl-3-cyanoquinolinium ion with N -methyl-9,10-dihydroacridine in acetonitrile
Hao, Weifang,Parker, Vernon D.
, p. 9286 - 9297 (2012)
A reinvestigation of the formal hydride transfer reaction of 1-benzyl-3-cyanoquinolinium ion (BQCN+) with N-methyl-9,10- dihydroacridine (MAH) in acetonitrile (AN) confirmed that the reaction takes place in more than one step and revealed a new mechanism that had not previously been considered. These facts are unequivocally established on the basis of conventional pseudo-first-order kinetics. It was observed that even residual oxygen under glovebox conditions initiates a chain process leading to the same products and under some conditions is accompanied by a large increase in the apparent rate constant for product formation with time. The efficiency of the latter process, when reactions are carried out in AN with rigorous attempts to remove air, is low but appears to be much more pronounced when MAH is the reactant in large excess. On the other hand, the intentional presence of air in AN ([air] = half-saturated) leads to a much greater proportion of the chain pathway, which is still favored by high concentrations of MAH. The latter observation suggests that a reaction intermediate reacts with oxygen to initiate the chain process in which MAH participates. Kinetic studies at short times show that there is no kinetic isotope effect on the initial step in the reaction, which is the same for the two competing processes. Our observation of the chain pathway of an NADH model compound under aerobic conditions is likely to be of importance in similar biological processes where air is always present.
DEHYDROGENATION OF FORMATE BY 10-METHYLACRIDINIUM ION
Hutchins, Jonathan E. C.,Binder, David A.,Kreevoy, Maurice M.
, p. 993 - 1006 (1986)
Formate is dehydrogenated to CO2 by 10-methylacridinium ion, mimicking formate dehydrogenase.The hydrogen and carbon kinetic isotope effects are 2.74 and 1.027 in a mixed solvent consisting of dimethylformamide and water in a 4 : 1 ratio, at 50 deg C.These values are similar to those observed in the enzymatic reaction (2.27 and 1.042, respectively) suggesting that the mechanisms of enzymatic and nonenzymatic reactions are the same, and transition state structures not too different.Marcus theory of atom and group transfer is used to locate the transition state for the nonenzymatic reaction 0.4 of the distance along the minimum energy path from precursor configuration to successor configuration.It is concluded, following Cleland and coworkers, that the protein of the enzyme dehydrates the formate and deforms the cofactor NAD+ so as to make the reaction more spontaneous.This produces an enzymatic transition state in which the covalency changes around hydrogen are less advanced than in the non-enzymatic transition state, but the environment of the carboxylate is much more suitable to the product, CO2.Yeast formate dehydrogenase brings about the oxidation of formate to CO2, in the process, transferring a hydride ion to the enzyme cofactor, Nicotinamide Adenine Dinucleotide (NAD+), reducing the latter to the corresponding 1,4-dihydropyridine, NADH (eq. 1) HCO2- + NAD+ ----> O2 + NADH Cleland and coworkers have made extensive studies of isotope effects on these reactions.They have shown that the reaction is essentially irreversible, and that the step involving the rearrangement of covalent bonds is fully rate-limiting.They have found that the NAD+ could be replaced with other pyridinium ions, and measured the changes in isotope effects which attended these replacements.They have found that N3- is a much more effective competitive inhibitor than NO3-.From these studies they have reached the following conclusions: 1.) Prior to the hydride transfer, the pyridinium ring is strongly distorted in the direction of dihydropyridine geometry, considerably increasing its hydride affinity (reduction potential). 2.) The transition state in the enzyme catalyzed reaction resembles the products much more closely than the reactants. 3.) Relatively small increases in the reduction potential of the cofactor significantly shift the transition state structure toward that of the reactants.Attempts to oxidize formate with simple NAD+ analogues have been unsuccessful but the reduction potential of 10-methylacridinium ion is -240 mv larger than that of NAD+ which should facilitate the reaction, according to Cleland's point 1.).Further, in refluxing formic acid solvent, formate has been shown to reduce 10-methylacridinium ion.We now report that formate is oxidized by 10-methylacridinium ion at measurable rates in both isopropanol (IPA) - water (4 : 1 by volume) and dimethylformamide (DMF) - water (4 :1 by volume) at 50 deg or 25 deg C. (2)HCOO- and H(13)COO- isotope effects have been measured and compared etc...............
Sequential electron-transfer and proton-transfer pathways in hydride-transfer reactions from dihydronicotinamide adenine dinucleotide analogues to non-heme oxoiron(IV) complexes and p-chloranil. Detection of radical cations of NADH analogues in acid-promoted hydride-transfer reactions
Fukuzumi, Shunichi,Kotani, Hiroaki,Lee, Yong-Min,Nam, Wonwoo
, p. 15134 - 15142 (2008)
Hydride transfer from dihydronicotinamide adenine dinucleotide (NADH) analogues, such as 10-methyl-9,10-dihydroacridine (AcrH2) and its derivatives, 1-benzyl-1,4-dihydronicotinamide (BNAH), and their deuterated compounds, to non-heme oxoiron(IV) complexes such as [(L)FeIV(O)] 2+ (L = N4Py, Bn-TPEN, and TMC) occurs to yield the corresponding NAD+ analogues and non-heme iron(II) complexes in acetonitrile. Hydride transfer from the NADH analogues to p-chloranil (Cl4Q) also occurs to produce the corresponding NAD+ analogues and the hydroquinone anion (Cl4QH-). The logarithms of the observed second-order rate constants (log kH) of hydride transfer from NADH analogues to non-heme oxoiron(IV) complexes are linearly correlated with those of hydride transfer from the same series of NADH analogues to Cl 4Q, including similar kinetic deuterium isotope effects. The log kH values of hydride transfer from NADH analogues to non-heme oxoiron(IV) complexes are also linearly correlated with those of deprotonation of the radical cations of NADH analogues. Such linear correlations indicate that overall hydride-transfer reactions of NADH analogues to both non-heme oxoiron(IV) complexes and Cl4Q occur via electron transfer from NADH analogues to the oxoiron(IV) complexes, followed by rate-limiting deprotonation from the radical cations of NADH analogues and subsequent rapid electron transfer from the deprotonated radicals to the Fe(III) complexes to yield the corresponding NAD+ analogues and the Fe(II) complexes. The electron-transfer pathway was accelerated by the presence of perchloric acid, and the resulting radical cations of NADH analogues were detected by electron spin resonance spectroscopy and UV-vis spectrophotometry in the acid-promoted hydride-transfer reactions from NADH analogues to non-heme oxoiron(IV) complexes. This result provides the first direct evidence that a hydride transfer from NADH analogues to non-heme oxoiron(IV) complexes proceeds via an electron-transfer pathway.
Structure and Reactivity of a Manganese(VI) Nitrido Complex Bearing a Tetraamido Macrocyclic Ligand
Shi, Huatian,Lee, Hung Kay,Pan, Yi,Lau, Kai-Chung,Yiu, Shek-Man,Lam, William W. Y.,Man, Wai-Lun,Lau, Tai-Chu
supporting information, p. 15863 - 15872 (2021/09/30)
Manganese complexes in +6 oxidation state are rare. Although a number of Mn(VI) nitrido complexes have been generated in solution via one-electron oxidation of the corresponding Mn(V) nitrido species, they are too unstable to isolate. Herein we report the isolation and the X-ray structure of a Mn(VI) nitrido complex, [MnVI(N)(TAML)]- (2), which was obtained by one-electron oxidation of [MnV(N)(TAML)]2- (1). 2 undergoes N atom transfer to PPh3 and styrenes to give Ph3P═NH and aziridines, respectively. A Hammett study for various p-substituted styrenes gives a V-shaped plot; this is rationalized by the ability of 2 to function as either an electrophile or a nucleophile. 2 also undergoes hydride transfer reactions with NADH analogues, such as 10-methyl-9,10-dihydroacridine (AcrH2) and 1-benzyl-1,4-dihydronicotinamide (BNAH). A kinetic isotope effect of 7.3 was obtained when kinetic studies were carried out with AcrH2 and AcrD2. The reaction of 2 with NADH analogues results in the formation of [MnV(N)(TAML-H+)]- (3), which was characterized by ESI/MS, IR spectroscopy, and X-ray crystallography. These results indicate that this reaction occurs via an initial "separated CPET"(separated concerted proton-electron transfer) mechanism; that is, there is a concerted transfer of 1 e- + 1 H+ from AcrH2 (or BNAH) to 2, in which the electron is transferred to the MnVI center, while the proton is transferred to a carbonyl oxygen of TAML rather than to the nitrido ligand.
Oxo-Free Hydrocarbon Oxidation by an Iron(III)-Isoporphyrin Complex
Doyle, Lorna M.,Farquhar, Erik R.,Gericke, Robert,Mcdonald, Aidan R.
supporting information, p. 13952 - 13961 (2020/10/09)
Metal-halides that perform proton coupled electron-transfer (PCET) oxidation are an important new class of high-valent oxidant. In investigating metal-dihalides, we reacted [FeIII(Cl)(T(OMe)PP)] (1, T(OMe)PP = meso-tetra(4-methoxyphenyl)porphyrinyl) with (dichloroiodo)benzene. An FeIII-meso-chloro-isoporphyrin complex [FeIII(Cl)2(T(OMe)PP-Cl)] (2) was obtained. 2 was characterized by electronic absorption, 1H NMR, EPR, and X-ray absorption spectroscopies and mass spectrometry with support from computational analyses. 2 was reacted with a series of hydrocarbon substrates. The measured kinetic data exhibited a nonlinear behavior, whereby the oxidation followed a hydrogen-atom-transfer (HAT) PCET mechanism. The meso-chlorine atom was identified as the HAT agent. In one case, a halogenated product was identified by mass spectrometry. Our findings demonstrate that oxo-free hydrocarbon oxidation with heme systems is possible and show the potential for iron-dihalides in oxidative hydrocarbon halogenation.
