Insights into Cytochrome P450 Enzyme Catalyzed Defluorination of Aromatic Fluorides

Density functional calculations establish a novel mechanism of aromatic defluorination by P450 Compound I. This is achieved via either an initial epoxide intermediate or through a 1,2-fluorine shift in an electrophilic intermediate, which highlights that the P450s can defluorinate fluoroarenes. However, in the absence of a proton donor a strong Fe-F bond can be obtained as shown from the calculations.

Alkylthio-tetrasubstituted μ-Nitrido Diiron Phthalocyanines: Spectroelectrochemistry, Electrical Properties, and Heterojunctions for Ammonia Sensing

Alkylthio-tetrasubstituted μ-nitrido diiron phthalocyanine complexes are synthesized with n-butyl, iso-butyl, tert-butyl, and n-hexadecyl alkyl moieties. For the first time, a spectroelectrochemical investigation of μ-nitrido diiron phthalocyanines is achieved at all the redox steps. The complexes are stable in all their redox states, unlike their unsubstituted analogues. The interest of the present complexes is to prepare sensing devices by a solution processing method. Films are characterized by electronic absorption and Raman spectroscopies. Electrical measurements on resistors show the highly resistive behavior of these complexes, whatever the chain length. However, when combined with the lutetium bisphthalocyanine, an intrinsic semiconductor, these complexes form heterojunctions that exhibit a high sensitivity to ammonia, with a very good signal over noise ratio, at room temperature and under atmospheric conditions.

Properties and reactivity of μ-nitrido-bridged dimetal porphyrinoid complexes: how does ruthenium compare to iron?

Methane hydroxylation by metal-oxo oxidants is one of the Holy Grails in biomimetic and biotechnological chemistry. The only enzymes known to perform this reaction in Nature are iron-containing soluble methane monooxygenase and copper-containing particulate methane monooxygenase. Furthermore, few biomimetic iron-containing oxidants have been designed that can hydroxylate methane efficiently. Recent studies reported that μ-nitrido-bridged diiron(IV)-oxo porphyrin and phthalocyanine complexes hydroxylate methane to methanol efficiently. To find out whether the reaction rates are enhanced by replacing iron by ruthenium, we performed a detailed computational study. Our work shows that the μ-nitrido-bridged diruthenium(IV)-oxo reacts with methane via hydrogen atom abstraction barriers that are considerably lower in energy (by about 5 kcal mol^‒1) as compared to the analogous diiron(IV)-oxo complex. An analysis of the electronic structure implicates similar spin and charge distributions for the diiron(IV)-oxo and diruthenium(IV)-oxo complexes, but the strength of the O‒H bond formed during the reaction is much stronger for the latter. As such a larger hydrogen atom abstraction driving force for the Ru complex than for the Fe complex is found, which should result in higher reactivity in the oxidation of methane.

Mechanism of Oxidative Activation of Fluorinated Aromatic Compounds by N-Bridged Diiron-Phthalocyanine: What Determines the Reactivity?

The biodegradation of compounds with C-F bonds is challenging due to the fact that these bonds are stronger than the C-H bond in methane. In this work, results on the unprecedented reactivity of a biomimetic model complex that contains an N-bridged diiron-phthalocyanine are presented; this model complex is shown to react with perfluorinated arenes under addition of H₂ O₂ effectively. To get mechanistic insight into this unusual reactivity, detailed density functional theory calculations on the mechanism of C₆ F₆ activation by an iron(IV)-oxo active species of the N-bridged diiron phthalocyanine system were performed. Our studies show that the reaction proceeds through a rate-determining electrophilic C-O addition reaction followed by a 1,2-fluoride shift to give the ketone product, which can further rearrange to the phenol. A thermochemical analysis shows that the weakest C-F bond is the aliphatic C-F bond in the ketone intermediate. The oxidative defluorination of perfluoroaromatics is demonstrated to proceed through a completely different mechanism compared to that of aromatic C-H hydroxylation by iron(IV)-oxo intermediates such as cytochrome P450 Compound I.

Carbene insertion to N–H bonds of 2-aminothiazole and 2-amino-1,3,4-thiadiazole derivatives catalyzed by iron phthalocyanine

Iron(III) phthalocyaninate decorated with crown ether substituents, [(15C5)4PcFe]Cl, efficiently catalyzed the insertion of carbene derived from ethyl diazoacetate to six amines functionalized with thiazole, thiazoline and thiadiazole heterocycles. The reactions were carried out under practical conditions using EDA:amine stoechiometric ratio with 0.05 mol% catalyst loading. Turnover numbers up to 3360 have been achieved. The aminoacid derivatives bearing heterocyclic moieties were obtained under catalytic conditions for the first time with 36–69% yields in the case of single N–H insertion products and up to 77% in the case of double N–H insertion products.

Electrocatalytic behavior of single walled carbon nanotubes with alkylthio-substituted cobalt binuclear phthalocyanines towards oxidation of 4-chlorophenols

This work describes the adsorption of synthesized cobalt mono (CoPc) and binuclear phthalocyanines (CoBiPc) with single walled carbon nanotubes (SWCNT) to form SWCNT-CoPc or SWCNT-CoBiPc as non-covalent conjugates onto glassy carbon electrodes (GCE). The cobalt complexes and their SWCNT-conjugate-modified electrodes were studied for their electrocatalytic oxidation towards 4-chlorophenol. All modified electrodes showed improved catalytic current and stability towards the detection of 4-chlorophenol. The best activity was observed for the SWCNT-CoBiPc2 system in terms of current response and the SWCNT-CoBiPc1 system in terms of resistance to electrode fouling.