Electron transfer at different electrode materials: Metals,semiconductors, and graphene

Electron transfer reactions are the most important processes at electrochemical interfaces. They are determined by the interplay between the interaction of the reactant with the solvent and the electronic levels of the electrode surface. Theoretical treatments only based on Density Functional Theory calculations are not sufficient. This review emphasizes mainly the effect of the electronic structure of the electrode material on electron transfer under different kinetic regimes. Our goal is to understand experimental results in the framework of a theory valid for arbitrary strengths of electronic coupling.     

Reduction of the Δ13-15-Keto Grouping of Prostaglandin Intermediates

In an attempt to gain further information on a stereo-structural model for activity of prostaglandins,² we undertook the synthesis of a number of new analogues.³ In particular, 17,17-dimethyl-F₂α was chosen as a good test of the “hairpin” conformation because the two 17-methyl groups would prevent side chain alignment in the particular sense of the “hairpin” model.⁴     

Direct Observation of an Oxepin from a Bacterial Cytochrome P450‐Catalyzed Oxidation

The cytochromes P450 are hemoproteins that catalyze a range of oxidative C?H functionalization reactions, including aliphatic and aromatic hydroxylation. These transformations are important in a range of biological contexts, including biosynthesis and xenobiotic biodegradation. Much work has been carried out on the mechanism of aliphatic hydroxylation, implicating hydrogen atom abstraction, but aromatic hydroxylation is postulated to proceed differently. One mechanism invokes as the key intermediate an arene oxide (and/or its oxepin tautomer). Conclusive isolation of this intermediate has remained elusive and, currently, direct formation of phenols from a Meisenheimer intermediate is believed to be favored. We report here the identification of a P450 [P450_cam (CYP101A1) and P450_cin (CYP176A1)]‐generated arene oxide as a product of in vitro oxidation of tert‐butylbenzene. Computations (CBS‐QB3) predict that the arene oxide and oxepin have similar stabilities to other arene oxides/oxepins implicated (but not detected) in P450‐mediated transformations, suggesting that arene oxides can be unstable terminal products of P450‐catalyzed aromatic oxidation that can explain the origin of some observed metabolites.     

SILYL- AND GERMYL-DIAZADIPHOSPHETIDINES

Abstract

Reaction of the 1,3,2,4-diazadiphosphetidine, trans-[C₆H₅N(H)P(S)NC₆H₅]₂ with LiR (R = Me, n-Bu) followed by treatment of the resulting dianions with Me₃SiCl and Me₃GeBr produced trans-[C₆H₅N(R)P(S)NC₆H₅]₂(R = Me₃Si, 2; Me₃Ge, 3). Substitution occurs without cis-trans isomerization or significant cleavage of the 1,3,2,4-diazadiphosphetidine ring. 2 and 3 have been characterized by spectral (¹H and ³¹P NMR, IR, and MS) and elemental analytical data. Analogous reactions involving Me₃SnCl yield mixtures containing [C₆H₅N(SnMe₃)P(S)NC₆H₅]₂ which could not be isolated or completely characterized.     

The Chemistry of 10-Pn-3 Systems1: Tricoordinate Hypervalent Pnictogen Compounds and Related Systems

Abstract

The unusual hypervalent tricoordinate pnictogen systems, 10-Pn-3 ADPnO, provide a convenient starting point for the study of a wide range of main group chemistry. Differences in reactivity patterns among the pnictogens are readily apparent from the variety of chemistry exhibited. The ADPnO systems also provide a model for the recently recognized edge inversion mechanism for 3 and 4 coordinate 8-electron main group species.