The rates of reduction of the diferric/radical center in mouse ribonucleotide reductase protein R2 were studied by light absorption and EPR in the native protein and in three point mutants of conserved residues involved in the proposed radical transfer pathway (D266A, W103Y) or in the unstructured C terminal domain (Y370W). The pseudo-first order rate constants for chemical reduction of the tyrosyl radical and diferric center by hydroxyurea, sodium dithionite or the dihydro form of flavin adenine dinucleotide, were comparable with or higher (particularly D266A, by dithionite) than in native R2. Molecular modeling of the D266A mutant showed that the iron/radical site should be more accessible for external reductants in the mutant than in native R2. The results indicate that no specific pathway is required for the reduction. The dihydro form of flavin adenine dinucleotide was found to be a very efficient reductant in the studied proteins compared to dithionite alone. The EPR spectra of the mixed-valent Fe(II)Fe(III) sites formed by chemical reduction in the D266A and W103Y mutants were clearly different from the spectrum observed in the native protein, indicating that the structure of the diferric site was affected by the mutations, as also suggested by the modeling study. No difference was observed between the mixed-valent EPR spectra generated by chemical reduction in Y370W mutant and native mouse R2 protein

Biomethane is a renewable fuel with a small environmental footprint. In its production, the removal of CO2 from the fermentation gas is critical. Pressure and vacuum swing adsorption (PSA and VSA) processes have certain advantages over other processes for the removal. Silicoaluminophosphate-56 (SAPO-56) has promising properties as an adsorbent for PSA- or VSA-based upgrading of raw biogas. It is typically synthesized by using N,N,N', N'-tetramethyl-1,6-hexanediamine (TMHD) as a structure directing agent (SDA). In this study, TMHD was partly replaced with three different low-cost templates: isopropylamine (IPA), dibutylamine, and tripropylamine. SAPO-56 was co-crystallized with mixtures of templating amines with up to a ratio of 30%:70% of TMHD:IPA. With using TMHD and IPA, small and defined crystals of SAPO-56 plus SAPO-47 formed instead of the large aggregates of SAPO-56 that formed when only TMHD was used. Solid-state 13C NMR spectroscopy was used to show that the IPA and TMHD had not been decomposed and that both molecules were included within the assynthesized crystals of SAPO-56. Synthetic composition diagrams were drawn with respect to the P2O5, SiO2, and Al2O3 compositions of the reaction mixtures and the formed crystalline SAPOs. In relation to these diagrams, the domains for stability of SAPO-56 were contrasted with those of SAPO-11, -17, -20, and -47. In particular, it was observed that SAPO-47 co-crystallized with SAPO-56 when a very large fraction of IPA was used under otherwise optimized conditions. As consistent with other studies, the SAPO-56 synthesized with dual SDAs had a very high uptake of CO2 at conditions relevant for PSA- or VSA-driven upgrading of raw biogas into methane.

The synthesis, structure and properties of two pentanuclear oxo-alkoxides are described. A combination of metathesis of LnCl(3) and 3KOPr(i) and stoichiometric hydrolysis resulted in the solvated oxo-alkoxide La5O(OPri)(13)(HOPri)(2) (1) and the non-solvated Ce5O(OPri)(13) (3). 1 is rather stable at room-temperature, but desolvation into La5O(OPri)(13) (2), identified by spectroscopy, could be achieved by vacuum treatment. 1 and 3 were structurally characterised by single-crystal X-ray diffraction. In both 1 and 3 the metal atoms have a square pyramidal arrangement. In 1, each crystallographically independent La5O(OPri)(13) (HOPri)(2) molecule contains 3 six-coordinated and 2 seven-coordinated La atoms, while in 3 all Ce atoms are six-coordinated. 3 Is the first structurally characterized example of a purely Ce3+ isopropoxide. Characterisations of 1 and 3 were by IR- and Raman spectroscopy and differential scanning calorimetry, and for 1 also by H-1 and C-13 NMR spectroscopy. The great similarity of the IR spectra of the solid 1 and 3, respectively, to their corresponding solutions, showed that the molecular structure present in the solid state is close to retained in solution.

Four new chiral pincer-complexes were prepared based on coupling of BINOL and TADDOL moieties with iodoresorcinol followed by oxidative addition of palladium(0). The X-ray analysis of complex 5a revealed that the BINOL rings form a well-defined chiral pocket around the palladium atom. This chiral environment can be further modified by γ-substitution of the BINOL rings. Preliminary studies for electrophilic allylation of sulfonimine 2 with allylstannane revealed that the presented chiral complexes are promising asymmetric catalysts for preparation of chiral homoallyl amines. The best result was achieved employing catalytic amounts of γ-Me BINOL complex 6 affording homoallyl amine 4 with 59% ee and 74% isolated yield.

Three novel complexes (mu-adt)[Fe-2(CO)(5)PTA] (2-PTA), (mu-adt)[Fe-2(CO)(4)PTA(2)](2-PTA(2)) and (mu-adt)[Fe-2(CO)(5)DAPTA] (2-DAPTA), where adt is SCH2N(CH2CH2CH3)CH2S, PTA stands for 1,3,5-triaza-7-phosphaadamantane and DAPTA is 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane, were prepared as the models of the iron hydrogenase active site through controlled CO displacement of (mu-adt)[Fe-2(CO)(6)] with PTA and DAPTA. The coordination configurations of 2-PTA and 2-PTA(2) were characterized by X-ray crystallography. The disubstituted diiron complex 2-PTA(2) features a basal/apical coordination mode, instead of the typical transoid basal/basal configuration. Protonation of three complexes only occurred at the bridging-N atom, rather than at the tertiary nitrogen atom on the PTA or DAPTA ligands. Electrochemical properties of the complexes were studied in acetonitrile or a mixture of acetonitrile and water in the presence of acetic acid, by cyclic voltammetry. The current sensitivity of the reduced species to acid concentration in the presence of H2O is greater than in the pure CH3CN solution.