scholarly journals An azobenzene container showing a definite folding – synthesis and structural investigation

2019 ◽  
Vol 15 ◽  
pp. 1534-1544
Author(s):  
Abdulselam Adam ◽  
Saber Mehrparvar ◽  
Gebhard Haberhauer
Keyword(s):  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Structural Investigation ◽  
Uv Light ◽  
Cd Spectroscopy ◽  
High Dispersion ◽  
Clockwise Rotation ◽  
Dispersion Energy ◽  
Different Types ◽  
Macrocyclic Peptides

The combination of photo-switchable units with macrocycles is a very interesting field in supramolecular chemistry. Here, we present the synthesis of a foldable container consisting of two different types of Lissoclinum macrocyclic peptides which are connected via two azobenzene units. The container is controllable by light: irradiation with UV light causes a switching process to the compact cis,cis-isomer, whereas by the use of visible light the stretched trans,trans-isomer is formed. By means of quantum chemical calculations and CD spectroscopy we could show that the trans→cis isomerization is spatially directed; that means that one of the two different macrocycles performs a definite clockwise rotation to the other, caused by irradiation with UV light. For the cis→trans isomerization counterclockwise rotations are found. Furthermore, quantum chemical calculations reveal that the energy of the cis,cis-isomer is only slightly higher than the energy of the cis,trans-isomer. This effect can be explained by the high dispersion energy in the compact cis,cis-isomer.

scholarly journals Azobenzene Container Showing a Definite Folding – Synthesis and Structural Investigation

2019 ◽  
Author(s):  
Abdulselam Adam ◽  
Saber Mehrparvar ◽  
Gebhard Haberhauer
Keyword(s):  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Structural Investigation ◽  
Uv Light ◽  
Cd Spectroscopy ◽  
High Dispersion ◽  
Clockwise Rotation ◽  
Dispersion Energy ◽  
Different Types ◽  
Macrocyclic Peptides

The combination of photo-switchable units with macrocycles is a very interesting field in supramolecular chemistry. Here, we present the synthesis of a foldable container consisting of two different types of Lissoclinum macrocyclic peptides which are connected via two azobenzene units. The container is controllable by light: Irradiation with UV light causes a switching process to the compact cis,cis isomer, whereas by the use of visible light the stretched trans,trans isomer is formed. By means of quantum chemical calculations and CD spectroscopy we could show that the trans→cis isomerization is spatially directed; that means that one of the two different macrocycles performs a definite clockwise rotation to the other, caused by irradiation with UV light. For the cis→trans isomerization counterclockwise rotations are found. Furthermore, quantum chemical calculations reveal that the energy of the cis,cis isomer is only slightly higher than the energy of the cis,trans isomer. This effect can be explained by the high dispersion energy in the compact cis,cis isomer.

Unravelling the fine structure of stacked bipyridine diamine-derived C3-discotics as determined by X-ray diffraction, quantum-chemical calculations, Fast-MAS NMR and CD spectroscopy

2011 ◽  
Vol 2 (1) ◽  
pp. 69-76 ◽  
Author(s):  
Thorsten Metzroth ◽  
Anke Hoffmann ◽  
Rafael Martín-Rapún ◽  
Maarten M. J. Smulders ◽  
Koen Pieterse ◽  
...  
Keyword(s):  
Fine Structure ◽  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Cd Spectroscopy ◽  
Mas Nmr ◽  
X Ray Diffraction ◽  
X Ray ◽  
Fast Mas

scholarly journals Thiocoumarin Caged Nucleotides: Synthetic Access and Their Photophysical Properties

Molecules ◽  
2020 ◽  
Vol 25 (22) ◽  
pp. 5325
Author(s):  
Jiahui Ma ◽  
Alexander Ripp ◽  
Daniel Wassy ◽  
Tobias Dürr ◽  
Danye Qiu ◽  
...  
Keyword(s):  
Controlled Release ◽  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Uv Light ◽  
Adenine Nucleotides ◽  
Photophysical Properties ◽  
Quantum Yields ◽  
Spatio Temporal

Photocages have been successfully applied in cellular signaling studies for the controlled release of metabolites with high spatio-temporal resolution. Commonly, coumarin photocages are activated by UV light and the quantum yields of uncaging are relatively low, which can limit their applications in vivo. Here, syntheses, the determination of the photophysical properties, and quantum chemical calculations of 7-diethylamino-4-hydroxymethyl-thiocoumarin (thio-DEACM) and caged adenine nucleotides are reported and compared to the widely used 7-diethylamino-4-hydroxymethyl-coumarin (DEACM) caging group. In this comparison, thio-DEACM stands out as a phosphate cage with improved photophysical properties, such as red-shifted absorption and significantly faster photolysis kinetics.

scholarly journals Vibrational Spectroscopy of Homo- and Heterochiral Amino Acid Dimers: Conformational Landscapes

Molecules ◽  
2021 ◽  
Vol 27 (1) ◽  
pp. 38
Author(s):  
Haolu Wang ◽  
Matthias Heger ◽  
Mohamad H. Al-Jabiri ◽  
Yunjie Xu
Keyword(s):  
Amino Acid ◽  
Quantum Chemical Calculations ◽  
Vibrational Spectroscopy ◽  
Quantum Chemical ◽  
Global Minimum ◽  
Spectroscopic Studies ◽  
Irmpd Spectroscopy ◽  
Infrared Multiple Photon Dissociation ◽  
Different Types ◽  
Conformational Spaces

The homo- and heterochiral protonated dimers of asparagine with serine and with valine were investigated using infrared multiple-photon dissociation (IRMPD) spectroscopy. Extensive quantum-chemical calculations were used in a three-tiered strategy to screen the conformational spaces of all four dimer species. The resulting binary structures were further grouped into five different types based on their intermolecular binding topologies and subunit configurations. For each dimer species, there are eight to fourteen final conformational geometries within a 10 kJ mol−1 window of the global minimum structure for each species. The comparison between the experimental IRMPD spectra and the simulated harmonic IR features allowed us to clearly identify the types of structures responsible for the observation. The monomeric subunits of the observed homo- and heterochiral dimers are compared to the corresponding protonated/neutral amino acid monomers observed experimentally in previous IRMDP/rotational spectroscopic studies. Possible chirality and kinetic influences on the experimental IRMPD spectra are discussed.

Discovery of a Difluoroglycine Synthesis Method through Quantum Chemical Calculations

2020 ◽  
Author(s):  
Tsuyoshi Mita ◽  
Yu Harabuchi ◽  
Satoshi Maeda
Keyword(s):  
Quantum Chemical Calculations ◽  
Experimental Verification ◽  
Quantum Chemical ◽  
Synthesis Method ◽  
Target Product ◽  
Systematic Exploration ◽  
Hands On ◽  
Retrosynthetic Analysis ◽  
Synthetic Routes ◽  
Verification Process

The systematic exploration of synthetic pathways to afford a desired product through quantum chemical calculations remains a considerable challenge. In 2013, Maeda et al. introduced ‘quantum chemistry aided retrosynthetic analysis’ (QCaRA), which uses quantum chemical calculations to search systematically for decomposition paths of the target product and propose a synthesis method. However, until now, no new reactions suggested by QCaRA have been reported to lead to experimental discoveries. Using a difluoroglycine derivative as a target, this study investigated the ability of QCaRA to suggest various synthetic paths to the target without relying on previous data or the knowledge and experience of chemists. Furthermore, experimental verification of the seemingly most promising path led to the discovery of a synthesis method for the difluoroglycine derivative. The extent of the hands-on expertise of chemists required during the verification process was also evaluated. These insights are expected to advance the applicability of QCaRA to the discovery of viable experimental synthetic routes.

Discovery of a Difluoroglycine Synthesis Method through Quantum Chemical Calculations

2020 ◽  
Author(s):  
Tsuyoshi Mita ◽  
Yu Harabuchi ◽  
Satoshi Maeda
Keyword(s):  
Quantum Chemical Calculations ◽  
Experimental Verification ◽  
Quantum Chemical ◽  
Synthesis Method ◽  
Target Product ◽  
Systematic Exploration ◽  
Hands On ◽  
Retrosynthetic Analysis ◽  
Synthetic Routes ◽  
Verification Process

The systematic exploration of synthetic pathways to afford a desired product through quantum chemical calculations remains a considerable challenge. In 2013, Maeda et al. introduced ‘quantum chemistry aided retrosynthetic analysis’ (QCaRA), which uses quantum chemical calculations to search systematically for decomposition paths of the target product and propose a synthesis method. However, until now, no new reactions suggested by QCaRA have been reported to lead to experimental discoveries. Using a difluoroglycine derivative as a target, this study investigated the ability of QCaRA to suggest various synthetic paths to the target without relying on previous data or the knowledge and experience of chemists. Furthermore, experimental verification of the seemingly most promising path led to the discovery of a synthesis method for the difluoroglycine derivative. The extent of the hands-on expertise of chemists required during the verification process was also evaluated. These insights are expected to advance the applicability of QCaRA to the discovery of viable experimental synthetic routes.

The Nature of Chemisorbed CO2 in Zeolite A

2019 ◽  
Author(s):  
Przemyslaw Rzepka ◽  
Zoltán Bacsik ◽  
Andrew J. Pell ◽  
Niklas Hedin ◽  
Aleksander Jaworski
Keyword(s):  
Solid State ◽  
Ir Spectroscopy ◽  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Surface Coverage ◽  
Gas Mixtures ◽  
Mas Nmr ◽  
Significant Fraction ◽  
Zeolite A

Formation of CO<sub>3</sub><sup>2-</sup> and HCO<sub>3</sub><sup>-</sup> species without participation of the framework oxygen atoms upon chemisorption of CO<sub>2</sub> in zeolite |Na<sub>12</sub>|-A is revealed. The transfer of O and H atoms is very likely to have proceeded via the involvement of residual H<sub>2</sub>O or acid groups. A combined study by solid-state <sup>13</sup>C MAS NMR, quantum chemical calculations, and <i>in situ</i> IR spectroscopy showed that the chemisorption mainly occurred by the formation of HCO<sub>3</sub><sup>-</sup>. However, at a low surface coverage of physisorbed and acidic CO<sub>2</sub>, a significant fraction of the HCO<sub>3</sub><sup>-</sup> was deprotonated and transformed into CO<sub>3</sub><sup>2-</sup>. We expect that similar chemisorption of CO<sub>2</sub> would occur for low-silica zeolites and other basic silicates of interest for the capture of CO<sub>2</sub> from gas mixtures.

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