Проектна діяльність бібліотек та інформаційних установ

Робоча навчальна програма «Проектна діяльність бібліотек та інформаційних установ» за напрямом підготовки 6.020102 «Книгознавство, бібліотекознавство і бібліографія», галузі знань 0201 «Культура», освітній рівень: перший (бакалаврський). - 2017 р

Laterally Mounted Azobenzenes on Platforms

Triazatriangulenium ions have previously been used as platforms to prepare self-assembled monolayers of functional molecules such as azobenzenes with vertical orientation and that are free-standing on gold surfaces. We have now prepared azobenzenes that are spanned between two posts which are attached on two platforms. Absorbed on a gold surface, the azobenzene should be laterally oriented at a distance of more than 4 Å above and thus electronically decoupled from the surface, and the system should perform a muscle-type movement upon isomerization

Insertion of Ni(I) into Porphyrins at Room Temperature: Preparation of Ni(II)porphyrins, and Ni(II)chlorins and Observation of Hydroporphyrin Intermediates

Reduced Nickel porphyrins play an important role as enzymatic cofactors in the global carbon cycle (cofactor F430), and as powerful catalysts in solar-to-fuel-processes such as the hydrogen evolution reaction, and the reduction of CO and CO₂. The preparation of Ni­(II)­porphyrins requires harsh conditions, and characterization of the reduced species is intricate. We present a very mild, convenient, and high yielding method of inserting Ni into electron rich, and electron deficient porphyrins which at the same time gives access to to Ni­(II) phlorins and Ni­(II)­chlorins and Ni­(II)­porphyrins

Doubly Coarctate-Stabilized Carbenes: Synthetic and Computational Studies

Isoindazoles joined by an ethynyl linker to either a phenyltriazene or a phenyldiazene moiety were synthesized, and their subsequent reactivity was examined. Computations suggest that these molecules could rearrange at moderate temperatures via carbene intermediates that are doubly stabilized by coarctate conjugation. The experimental results corroborate the calculations, as the transient carbene can either be trapped with oxygen or undergo ring-opening to afford a rearranged product. Additional calculations illustrate some design principles that might lead to stable carbenes that are the global minimum on the coarctate hypersurface

Modular Synthetic Route to Monofunctionalized Porphyrin Architectures

The synthesis of a borylated Ni²⁺ porphyrin and its application as a versatile precursor for building up functional <i>ortho</i>-substituted tetraaryl porphyrin architectures is reported. This precursor porphyrin provides the basis for efficient modular syntheses of porphyrin compounds with covalently attached axial ligands which are important as enzyme model complexes, electron transfer dyads, and many other applications. In the present study, the precursor porphyrin was used for the synthesis of molecular spin switches which previously showed high potential as photoresponsive contrast agents for magnetic resonance imaging

Design and Synthesis of Photodissociable Ligands Based on Azoimidazoles for Light-Driven Coordination-Induced Spin State Switching in Homogeneous Solution

Light-switchable azoimidazoles were rationally designed and synthesized, and their performance was investigated as photodissociable ligands (PDL) and for spin state switching of Ni porphyrins. The rationally designed ligands exhibit a high photochemical conversion rate (<i>trans</i> → <i>cis</i> > 98%) and no measurable fatigue over a large number of switching cycles at room temperature under air. As compared to the known phenylazopyridines, the phenylazoimidazoles exhibit a much stronger affinity as axial ligands to Ni porphyrin in the binding <i>trans</i> configuration and a low affinity in their <i>cis</i> form. This affinity switching was used to control the coordination number of Ni²⁺. Concomitant with the change in coordination number is the change of the spin state from triplet (high spin) to singlet state (low spin). We report on phenylazoimidazole-based PDLs that switch the paramagnetic ratio of the investigated nickel species by up to 70%. Consequently, azoimidazoles exhibit considerably higher switching efficiencies than previously described pyridine-based PDLs

Exceptionally Mild and High-Yielding Synthesis of Vinyl Esters of Alpha-Ketocarboxylic Acids, Including Vinyl Pyruvate, for Parahydrogen-Enhanced Metabolic Spectroscopy and Imaging

Metabolic changes often occur long before pathologies manifest and treatment becomes challenging. As key elements of energy metabolism, α-ketocarboxylic acids (α-KCA) are particularly interesting, e.g., as the upregulation of pyruvate to lactate conversion is a hallmark of cancer (Warburg effect). Magnetic resonance imaging with hyperpolarized metabolites has enabled imaging of this effect non-invasively and in vivo, allowing the early detection of cancerous tissue and its treatment. Hyperpolarization by means of dynamic nuclear polarization, however, is complex, slow, and expensive, while available precursors often limit parahydrogen-based alternatives. Here, we report the synthesis for novel 13C, deuterated ketocarboxylic acids, and a much-improved synthesis of 1-13C-vinyl pruvate-d6, arguably the most promising tracer for hyperpolarizing pyruvate using parahydrogen-induced hyperpolarization by side arm hydrogenation. The new synthesis is scalable and provides a high yield of 52%. We elucidated the mechanism of our Pd-catalyzed trans-vinylation reaction. Hydrogenation with parahydrogen allowed us to monitor the addition, which was found to depend on the electron demand of the vinyl ester. Electron-poor α-keto vinyl esters react slower than “normal” alkyl vinyl esters. This synthesis of 13C, deuterated α-ketocarboxylic acids opens up an entirely new class of biomolecules for fast and cost-efficient hyperpolarization with parahydrogen and their use for metabolic imaging

Photoswitching in Two-Component Surface-Mounted Metal–Organic Frameworks: Optically Triggered Release from a Molecular Container

The remote control of surface properties is one of the key challenges in interfacial systems chemistry. Here, we report the realization of a SURMOF (surface-mounted metal–organic framework)-based hybrid system in which a crucial component can be switched by light. The realization of this two-component system is made possible by installing vertical compositional gradients <i>via</i> liquid-phase epitaxy. After loading the porous coating with guest molecules, its release is initiated by illumination with visible light and monitored by a quartz crystal microbalance

Exceptionally Mild and High-Yielding Synthesis of Vinyl Esters of Alpha-Ketocarboxylic Acids, Including Vinyl Pyruvate, for Parahydrogen-Enhanced Metabolic Spectroscopy and Imaging

Metabolic changes often occur long before pathologies manifest and treatment becomes challenging. As key elements of energy metabolism, α-ketocarboxylic acids (α-KCA) are particularly interesting, e.g., as the upregulation of pyruvate to lactate conversion is a hallmark of cancer (Warburg effect). Magnetic resonance imaging with hyperpolarized metabolites has enabled imaging of this effect non-invasively and in vivo, allowing the early detection of cancerous tissue and its treatment. Hyperpolarization by means of dynamic nuclear polarization, however, is complex, slow, and expensive, while available precursors often limit parahydrogen-based alternatives. Here, we report the synthesis for novel 13C, deuterated ketocarboxylic acids, and a much-improved synthesis of 1-13C-vinyl pruvate-d6, arguably the most promising tracer for hyperpolarizing pyruvate using parahydrogen-induced hyperpolarization by side arm hydrogenation. The new synthesis is scalable and provides a high yield of 52%. We elucidated the mechanism of our Pd-catalyzed trans-vinylation reaction. Hydrogenation with parahydrogen allowed us to monitor the addition, which was found to depend on the electron demand of the vinyl ester. Electron-poor α-keto vinyl esters react slower than “normal” alkyl vinyl esters. This synthesis of 13C, deuterated α-ketocarboxylic acids opens up an entirely new class of biomolecules for fast and cost-efficient hyperpolarization with parahydrogen and their use for metabolic imaging

Coordination-Induced Spin-State Switching with Nickel Chlorin and Nickel Isobacteriochlorin

We present the first coordination-induced spin-state switching with nickel chlorin and nickel isobacteriochlorin. The spin-state switching was monitored by UV–vis spectroscopy and NMR titration experiments. The association constants (<i>K</i>₁ and <i>K</i>₂) and thermodynamic parameters (Δ<i>H</i> and Δ<i>S</i>) of the coordination of pyridine were determined. The first X-ray analyses of a paramagnetic nickel chlorin and a nickel isobacteriochlorin provide further information about the structure of the octahedral complexes. Nickel chlorin and even more pronounced nickel isobacteriochlorin exhibit stronger coordination of axial ligands compared to the corresponding nickel porphyrin and thus provide the basis for more efficient spin-switching systems