Evaluation of the 3rd Order Perturbations for the Degenerate Cases

In the calculation of quantum systems in most cases, the perturbation theory is used. Lot of calculation techniques are used for both (nondegenerate and degenerate) cases. In our contribution we evaluate the projection operator technique in such case when the Hamiltonian of the given quantum system has point spectrum with finite degree of degeneracy.     

Stereoselective aldol additions catalyzed by dihydroxyacetone phosphate-dependent aldolases in emulsion systems: preparation and structural characterization of linear and cyclic iminopolyols from aminoaldehydes

The potential of dihydroxyacetone phosphate (DHAP)-dependent aldolases to catalyze stereoselective aldol additions is, in many instances, limited by the solubility of the acceptor aldehyde in aqueous/co-solvent mixtures. Herein, we demonstrate the efficiency of emulsion systems as reaction media for the class I fructose-1,6-bisphosphate aldolase (RAMA) and class II recombinant rhamnulose-1-phosphate aldolase from E. coli (RhuA)-catalyzed aldol addition between DHAP and N-benzyloxycarbonyl (N-Cbz) aminoaldehydes. The use of emulsions improved the RAMA-catalyzed aldol conversions by three to tenfold relative to those in conventional DMF/water mixtures. RhuA was more reactive than RAMA towards the N-Cbz aminoaldehydes regardless of the reaction medium. With (S)- or (R)-Cbz-alaninal, RAMA exhibited preference for the R enantiomer, while RhuA had no enantiomeric discrimination. The linear N-Cbz aminopolyols thus obtained were submitted to catalytic intramolecular reductive amination to afford the corresponding iminocyclitols. This reaction was diastereoselective in all cases examined; the face selectivity was controlled by the stereochemistry of the newly formed hydroxyl group originating from the aldehyde. Characterization of the resulting iminocyclitols allowed the assessment of the diastereoselectivity of the enzymatic aldol reactions with respect to the N-protected aminoaldehyde. RAMA formed single diastereoisomers from N-Cbz-glycinal and from both enantiomers of N-Cbz-alaninal, while 14 % of the epimeric product was observed from N-Cbz-3-aminopropanal. Diastereoselectivity from RhuA was lower than that observed from RAMA. Interestingly, a single diastereoisomer was formed from (S)-Cbz-alaninal, whereas only a 34 % diastereomeric excess was observed from its enantiomer (i.e., (R)-Cbz-alaninal).     

Technische Verfahren zur Synthese von Carotinoiden und verwandten Verbindungen aus 6-Oxo-isophoron. VI. Synthese Von Rhodoxanthin und (3-RS, 3′RS)-Zeaxanthin; Zugänge zur C15-Ringkomponente über 3-Oxo-jonon-Derivate

Technical Procedures for the Synthesis of Carotenoids and Related Compounds from 6-Oxo-isophorone, VI. Synthesis of Rhodoxanthin and (3RS, 3′RS)-Zeaxanthin; Routes to the C₁₅-Ring Component via 3-Oxo-ionone Derivatives The C₁₅-ring component 4 , key intermediate of a new scheme for the synthesis of rhodoxanthin ( 1 ) and (3RS, 3RS)-zeaxanthin ( 3 ), has been synthesized starting from 6-oxo-isophorone ( 7 ) via 3-oxo-cyclocitral and 3-oxo-ionone derivatives.     

Fine-tuning the electronic properties of highly stable organometallic Cu(III) complexes containing monoanionic macrocyclic ligands

A family of highly stable organometallic Cu(III) complexes with monoanionic triazamacrocyclic ligands (L(i)) with general formula [CuL(i)]+ have been prepared and isolated, and their structural, spectroscopic, and redox properties thoroughly investigated. The HL(i) ligands have been designed in order to understand and quantify the electronic effects exerted by electron donor and electron-withdrawing groups on either the aromatic ring or the central secondary amine or on both. In the solid state the Cu(III) complexes were mainly characterized by single-crystal X-ray diffraction analysis, whereas in solution their structural characterization was mainly based on 1H NMR spectroscopy given the diamagnetic nature of the d(8) square-planar Cu(III) complexes. Cyclic voltammetry together with 1H NMR and UV/Vis spectroscopy have allowed us to quantify the electronic effects exerted by the ligands on the Cu(III) metal center. A theoretical analysis of this family of Cu(III) complexes has also been undertaken by DFT calculations to gain a deeper insight into the electronic structure of these complexes, which has in turn allowed a greater understanding of the nature of the UV/Vis transitions as well as the molecular orbitals involved.     

Simultaneous measurement of J(HH) and two different nJ(CH) coupling constants from a single multiply edited 2D cross‐peak

Three different J‐editing methods (IPAP, E.COSY and J‐resolved) are implemented in a single NMR experiment to provide spin‐state‐edited 2D cross‐peaks from which a simultaneous measurement of different homonuclear and heteronuclear coupling constants can be performed. A new J‐selHSQMBC‐IPAP experiment is proposed for the independent measurement of two different ⁿJ(CH) coupling constants along the F2 and F1 dimensions of the same 2D cross‐peak. In addition, the E.COSY pattern provides additional information about the magnitude and relative sign between J(HH) and ⁿJ(CH) coupling constants. Copyright © 2013 John Wiley & Sons, Ltd.     

meso‐Ester Corroles

The introduction of ester groups on the 5‐ and 15‐meso positions of corroles stabilizes them against oxidation and induces a redshift of their absorption and emission spectra. These effects are studied through the photophysical and electrochemical characterization of up to 16 different 5,15‐diester corroles, in which the third meso position is free or occupied by an aryl group, a long alkyl chain, or an ester moiety. Single‐crystal X‐ray structure analysis of five 5,15‐diestercorroles and DFT and time‐dependent DFT calculations show that the strong electron‐withdrawing character of the 5,15 ester substituents is reinforced by their π overlap with the macrocyclic aromatic system. The crystal packing of corroles 2 , 4 , 6 , 9 , and 15 features short distances between chromophores that are stacked into columns thanks to the low steric hindrance of meso‐ester groups. This close packing is partially due to intermolecular interactions that involve inner hydrogen and nitrogen atoms, and thereby, stabilize a single, identical corrole tautomeric form.     

On the interference of J(HH) modulation in HSQMBC‐IPAP and HMBC‐IPAP experiments

The effects of phase modulation due to homonuclear proton–proton coupling constants in HSQMBC‐IPAP and HMBC‐IPAP experiments are experimentally evaluated. We show that accurate values of small proton–carbon coupling constants, ⁿJ_CH, can be extracted even for phase‐distorted cross‐peaks obtained from a selHSQMBC experiment applied simultaneously on two mutually J‐coupled protons. On the other hand, an assessment of the reliability of ⁿJ_CH measurement from distorted cross‐peaks obtained in broadband IPAP versions of equivalent HMBC and HSQMBC experiments is also presented. Finally, we show that HMBC‐COSY experiments could be an excellent complement to HMBC for the measurement of small ⁿJ_CH values. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of Hydrodynamic Forces on meso‐(4‐Sulfonatophenyl)‐Substituted Porphyrin J‐Aggregate Nanoparticles: Elasticity,Plasticity and Breaking

The J aggregates of 4‐sulfonatophenyl meso‐substituted porphyrins are non‐covalent polymers obtained by self‐assembly that form nanoparticles of different morphologies. In the case of high aspect‐ratio nanoparticles (bilayered ribbons and monolayered nanotubes), shear hydrodynamic forces may modify their shape and size, as observed by peak force microscopy, transmission electron microscopy of frozen solutions, small‐angle X‐ray scattering measurements in a disk‐plate rotational cell, and cone–plate rotational viscometry. These nanoparticles either show elastic or plastic behaviour: there is plasticity in the ribbons obtained upon nanotube collapse on solid/air interfaces and in viscous concentrated nanotube solutions, whereas elasticity occurs in the case of dilute nanotube solutions. Sonication and strong shear hydrodynamic forces lead to the breaking of the monolayered nanotubes into small particles, which then associate into large colloidal particles.