The trials and triumphs of modelling X-ray absorption spectra of transition metal phthalocyanines.

This study explores the electronic structure of Co, Fe and Mn phthalocyanines (TMPcs) as well as their perfluorinated counterparts through a series of electronic structure calculations utilizing multireference methods and by simulating their metal L-edge and ligand (nitrogen and fluorine) K-edge X-ray absorption spectra (XAS) in an angle-resolved manner. Simulations targeting different ground-state symmetries, where relevant, have been conducted to observe changes in the N K-edge lineshape. The applicability of the quasi-degenerate formulation of -electron valence state perturbation theory (QD-NEVPT2) for L-edge X-ray absorption spectroscopy (XAS) is evaluated, alongside the use of a restricted active space (RAS) formalism to describe the final-state multiplets generated by L-shell X-ray processes.

Oxygen sensitivity of [FeFe]-hydrogenase: a comparative study of active site mimics inside outside the enzyme.

[FeFe]-hydrogenase is nature's most efficient proton reducing and H-oxidizing enzyme. However, biotechnological applications are hampered by the O sensitivity of this metalloenzyme, and the mechanism of aerobic deactivation is not well understood. Here, we explore the oxygen sensitivity of four mimics of the organometallic active site cofactor of [FeFe]-hydrogenase, [Fe(adt)(CO)(CN)] and [Fe(pdt)(CO)(CN)] ( = 1, 2) as well as the corresponding cofactor variants of the enzyme by means of infrared, Mössbauer, and NMR spectroscopy.

A CuCo cryptate for the visible light-driven reduction of CO.

Among the rare bimetallic complexes known for the reduction of CO, CoCo and ZnCo hexamine cryptates are described as efficient photocatalysts. In close relation to the active sites of natural, CO-reducing enzymes, we recently reported the asymmetric cryptand {NN} ({NN} = N[(CH)SCH(-CH)CHNH(CH)]N) comprising distinct sulphur- and nitrogen-rich binding sites and the corresponding CuM (M = Co, Ni, Cu) complexes. To gain insight into the effect of metals in different oxidation states and sulphur-incorporation on the photocatalytic activity, we herein investigate the CuCo complex of {NN} as catalyst for the visible light-driven reduction of CO.

Asymmetric Synthesis of 3,4-Disubstituted 2-(Trifluoromethyl)pyrrolidines through Rearrangement of Chiral 2-(2,2,2-Trifluoro-1-hydroxyethyl)azetidines.

Enantiopure 4-formyl-β-lactams were deployed as synthons for the diastereoselective formation of chiral 2-(2,2,2-trifluoro-1-hydroxyethyl)azetidines via trifluoromethylation through aldehyde modification followed by reductive removal of the β-lactam carbonyl moiety. Subsequent treatment of the (in situ) activated 2-trifluoroethylated azetidines with a variety of nitrogen, oxygen, sulfur, and fluorine nucleophiles afforded chiral 3,4-disubstituted 2-(trifluoromethyl)pyrrolidines in good to excellent yields (45-99%) and high diastereoselectivities (dr >99/1, H NMR) via interception of bicyclic aziridinium intermediates. Furthermore, representative pyrrolidines were N,O-debenzylated in a selective way and used for further synthetic elaboration to produce, for example, a CF-substituted 2-oxa-4,7-diazabicyclo[3.

Tandem Addition of Phosphite Nucleophiles Across Unsaturated Nitrogen-Containing Systems: Mechanistic Insights on Regioselectivity.

The addition of phosphite nucleophiles across linear unsaturated imines is a powerful and atom-economical methodology for the synthesis of aminophosphonates. These products are of interest from both a biological and a synthetic point of view: they act as amino acid transition state analogs and Horner-Wadsworth-Emmons reagents, respectively. In this work the reaction between dialkyl trimethylsilyl phosphites and α,β,γ,δ-diunsaturated imines was evaluated as a continuation of our previous efforts in the field.