153 results on '"Takashiro Akitsu"'
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2. Crystal structure and Hirshfeld surface analysis of (1H-imidazole-κN3)[4-methyl-2-({[2-oxido-5-(2-phenyldiazen-1-yl)phenyl]methylidene}amino)pentanoate-κ3O,N,O′]copper(II)
- Author
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Ai Kaneda, Soma Suzuki, Daisuke Nakane, Yukiyasu Kashiwagi, and Takashiro Akitsu
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schiff base ligand ,copper(ii) complex ,amino acid ,azobenzene ,hirshfeld analysis ,crystal structure ,Crystallography ,QD901-999 - Abstract
The title copper(II) complex, [Cu(C18H19N3O3)(C3H4N2)], consists of a tridentate ligand synthesized from L-leucine and azobenzene-salicylaldehyde. One imidazole molecule is additionally coordinated to the copper(II) ion in the equatorial plane. The crystal structure features N—H...O hydrogen bonds. A Hirshfeld surface analysis indicates that the most important contributions to the packing are from H...H (52.0%) and C...H/H...C (17.9%) contacts.
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- 2024
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3. The prediction of single-molecule magnet properties via deep learning
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Yuji Takiguchi, Daisuke Nakane, and Takashiro Akitsu
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single-molecule magnets ,deep learning ,cambridge structural database ,salen-type complexes ,Crystallography ,QD901-999 - Abstract
This paper uses deep learning to present a proof-of-concept for data-driven chemistry in single-molecule magnets (SMMs). Previous discussions within SMM research have proposed links between molecular structures (crystal structures) and single-molecule magnetic properties; however, these have only interpreted the results. Therefore, this study introduces a data-driven approach to predict the properties of SMM structures using deep learning. The deep-learning model learns the structural features of the SMM molecules by extracting the single-molecule magnetic properties from the 3D coordinates presented in this paper. The model accurately determined whether a molecule was a single-molecule magnet, with an accuracy rate of approximately 70% in predicting the SMM properties. The deep-learning model found SMMs from 20 000 metal complexes extracted from the Cambridge Structural Database. Using deep-learning models for predicting SMM properties and guiding the design of novel molecules is promising.
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- 2024
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4. Azobenzene-Containing Schiff-Bases—Syntheses and Dyes Applications
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Estelle Leonard, China Takeda, and Takashiro Akitsu
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Azo-Schiff bases ,sensors ,liquid crystals ,antibacterials ,fuel cells ,Chemistry ,QD1-999 - Abstract
Azo-Schiff bases contain an azo photochrome showing isomerization accompanying with color change, and an imine moiety (which can contribute to the metal complexation capability). The syntheses of these molecules will be described, and their dyes applications will be discussed, such as for fuel cells, as photometric or colorimetric sensors. In addition, liquid crystals and their antibacterial efficiencies will also be discussed.
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- 2024
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5. Toward flame retardants or thermal stabilizers with new mechanism for polymers
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Takashiro Akitsu, Akinori Honda, Taiga Imae, and Yuya Higashi
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Polymer ,Flame retardants ,Thermal stabilizers ,Phase transition ,Cold crystallization ,Explosives and pyrotechnics ,TP267.5-301 - Abstract
This review discusses conventional flame retardants for polymers and the possibility of using endothermal materials as flame retardants. Halogen-based, phosphorus-based, inorganic compounds, and their combinations are generally used as flame retardants for polymeric materials. The mechanism of action involves the trapping of radicals in the gas phase, an endothermic dehydration reaction, the blocking of oxygen, and a heat insulation effect by char in the solid phase. We discuss the possibility of using low-molecular-weight organic (or inorganic) metal complexes, exhibiting unique endothermic phenomena, such as phase transitions and cold crystallization, as flame retardants or thermal stabilizers at lower temperatures. In addition, this review provides an outlook on state-of-the-art) polymer flame-retardant technology.
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- 2023
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6. Inversely Finding Peculiar Reaction Conditions toward Microfluidic Droplet Synthesis
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Takashiro Akitsu
- Subjects
microfluidics ,microdroplet ,metal complexes ,preparation ,reaction condition ,Chemistry ,QD1-999 - Abstract
With the development of microfluidics, there are increasing reports of syntheses using not only conventional laminar flow at the microscale, but also the dissociation and aggregation of microdroplets. It is known, to some extent, that the microfluidics scale differs from normal scales in terms of the specific surface area, mass diffusion, and heat conduction; these are opposite to those in scale-up in-plant chemical engineering. However, it is not easy to determine what changes when the microdroplet flows through the channel. In this context, the author would like to clarify how the behavior of chemical species, which is expected to appear unique at the nanoscale, contributes to chemical reactions. What do we need in order to develop a completely new theory of chemical reactions? The characteristics of chemical reactions on the nanoscale are clarified via the encountering of solutions by the microfluidic device itself, or the chemical reaction of nanoscale droplets generated by the microfluidic device. Specifically, in recent years, experimental reports have accumulated that are expected to develop a fluidic device that can stably generate nanodroplets, and complex reactions of different reactivity are expected to occur that are specific to the nanoscale. In this short article, microfluidic devices, nanoscale droplets, experimental synthetic examples, and findings that may provide solutions are described.
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- 2023
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7. Improvement of the SOD activity of the Cu2+ complexes by hybridization with lysozyme and its hydrogen bond effect on the activity enhancement
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Daisuke Nakane, Yukihito Akiyama, Soma Suzuki, Ryotaro Miyazaki, and Takashiro Akitsu
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Cu2+ complex ,SOD activity ,hybrid protein ,lysozyme ,hydrogen bond ,Chemistry ,QD1-999 - Abstract
We prepared L-amino acids (L-valine and L-serine, respectively) based on the Schiff base Cu2+ complexes CuSV and CuSS in the absence/presence of hydroxyl groups and their imidazole-bound compounds CuSV-Imi and CuSS-Imi to reveal the effects of hydroxyl groups on SOD activity. The structural and spectroscopic features of the Cu2+ complexes were evaluated using X-ray crystallography, UV-vis spectroscopy, and EPR spectroscopy. The spectroscopic behavior upon addition of lysozyme indicated that both CuSV and CuSS were coordinated by the imidazole group of His15 in lysozyme at their equatorial position, leading to the formation of hybrid proteins with lysozyme. CuSS-Imi showed a higher SOD activity than CuSV-Imi, indicating that the hydroxyl group of CuSS-Imi played an important role in the disproportionation of O2− ion. Hybridization of the Cu2+ complexes CuSV and CuSS with lysozyme resulted in higher SOD activity than that of CuSV-Imi and CuSS-Imi. The improvements in SOD activity suggest that there are cooperative effects between Cu2+ complexes and lysozyme.
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- 2024
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8. Crystal structure and Hirshfeld surface analysis of (1H-imidazole-κN3)[N-(2-oxidobenzylidene)tyrosinato-κ3O,N,O′]copper(II)
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Soma Suzuki, Yukihito Akiyama, Daisuke Nakane, and Takashiro Akitsu
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schiff base complex ,copper ,amino acid ,hirshfeld analysis ,crystal structure ,Crystallography ,QD901-999 - Abstract
The title copper(II) complex, [Cu(C16H13NO4)(C3H4N2)], consists of a tridentate ligand synthesized from L-tyrosine and salicylaldehyde. One imidazole molecule is additionally coordinating to the copper(II) ion. The crystal structure features N—H...O, O—H...O and C—H...O hydrogen bonds. The Hirshfeld surface analysis indicates that the most important contributions to the packing are from H...H (37.9%), C...H (28.2%) and O...H/H...O (21.2%) contacts.
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- 2023
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9. Verification of the Inverse Scale Effect Hypothesis on Viscosity and Diffusion by Azo-Amino Acid Schiff Base Copper Complexes
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Yoshitora Wadayama, Ai Kaneda, Taiga Imae, Daisuke Nakane, and Takashiro Akitsu
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viscosity ,diffusion ,solvent ,Schiff base complex ,azobenzene ,Technology ,Science - Abstract
Microdroplets generated in microfluidic devices are attracting attention as a new chemical reaction field and are expected to improve reactivity. One of the effects of microscaling is that the ratio of the force that acts on the diffusion and movement of substances to gravity is different from that of ordinary solvents. Recently, we proposed a hypothesis for determining reaction acceleration through micro-miniaturization: If a reaction is inhibited by setting the volume and viscosity of the solution to conditions that are unfavorable to the reaction on a normal scale, that reaction can be promoted in microfluidics. Therefore, for the purpose of this verification, (1) we used an amino acid Schiff base copper(II) complex with an azobenzene group to demonstrate the polarization-induced orientation in a polymer film (the redirection that is mechanically maintained in a soft matter matrix). Numerical data on optical anisotropy parameters were reported. (2) When the reaction is confirmed to be promoted in laminar flow in a microfluidic device and its azo derivative, a copper(II) complex is used to increase the solvent viscosity or diffusion during synthesis on a normally large scale. We will obtain and discuss data on the investigation of changing the solvent volume as a region. The range of experimental conditions for volume and viscosity did not lead to an improvement in synthetic yield, nor did (3) the comparison of solvents and viscosity for single-crystal growth of amino acid Schiff base copper(II) complexes having azobenzene groups. A solvent whose viscosity was measured was used, but microcrystals were obtained using the diffusion method.
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- 2024
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10. Efficient Separation of Methanol Single-Micron Droplets by Tailing Phenomenon Using a PDMS Microfluidic Device
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Daiki Tanaka, Shengqi Zheng, Masahiro Furuya, Masashi Kobayashi, Hiroyuki Fujita, Takashiro Akitsu, Tetsushi Sekiguchi, and Shuichi Shoji
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organic microdroplets ,single-micron droplets ,fluid control ,surface treatment ,Organic chemistry ,QD241-441 - Abstract
Microdroplet-based fluidic systems have the advantages of small size, short diffusion time, and no cross-contamination; consequently, droplets often provide a fast and precise reaction environment as well as an analytical environment for individual molecules. In order to handle diverse reactions, we developed a method to create organic single-micron droplets (S-MDs) smaller than 5 μm in diameter dispersed in silicone oil without surfactant. The S-MD generation microflow device consists of a mother droplet (MoD) generator and a tapered separation channel featuring multiple side channels. The tapered channel enhanced the shear forces to form tails from the MoDs, causing them to break up. Surface treatment with the fluoropolymer CYTOP protected PDMS fluid devices from organic fluids. The tailing separation of methanol droplets was accomplished without the use of surfactants. The generation of tiny organic droplets may offer new insights into chemical separation and help study the scaling effects of various chemical reactions.
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- 2024
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11. Nanoframes as a Resilient Candidate for a Broader Spectra of Catalysis Challenges
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Fawad Ahmad, Qurat ul Ain, Shafaq Zahid, and Takashiro Akitsu
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Nanoframes ,catalysis ,ORR ,HER ,FAOR ,detection of tumor cell ,Mathematics ,QA1-939 - Abstract
Metal nanoframes have gained tremendous attention in the domain of modern research and development due to their distinctive 3D spatial structure, efficient physiochemical properties, and comparatively good activity. Different strategies have been implicated by the researchers to design nanoframes of varying chemical natures and shapes. Most of the synthetic protocols being adopted to design nanoframes consist of two main steps: nucleation and the growth of solid particles and, secondly, excavation of the interiors. In this context, many synthetic methods are overviewed. To show their unprecedented performance or activity, a few applications in catalysis, biomedicine, theranostics, SERS, the sensing of different materials, the reduction of CO2, etc., are also discussed.
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- 2024
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12. Chemistry for Space Group Symmetry beyond Crystals
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Takashiro Akitsu, Yuya Higashi, Rin Tsuchiya, Taiga Imae, Keishiro Komatsu, Daisuke Nakane, and Dohyun Moon
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n/a ,Mathematics ,QA1-939 - Abstract
As a recent cutting-edge research target, the prediction of crystal systems or space groups using machine learning based on databases has been actively reported [...]
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- 2024
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13. A novel hybrid protein composed of superoxide-dismutase-active Cu(II) complex and lysozyme
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Tetsundo Furuya, Daisuke Nakane, Kenichi Kitanishi, Natsuki Katsuumi, Arshak Tsaturyan, Igor N. Shcherbakov, Masaki Unno, and Takashiro Akitsu
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Medicine ,Science - Abstract
Abstract A novel hybrid protein composed of a superoxide dismutase-active Cu(II) complex (CuST) and lysozyme (CuST@lysozyme) was prepared. The results of the spectroscopic and electrochemical analyses confirmed that CuST binds to lysozyme. We determined the crystal structure of CuST@lysozyme at 0.92 Å resolution, which revealed that the His15 imidazole group of lysozyme binds to the Cu(II) center of CuST in the equatorial position. In addition, CuST was fixed in position by the weak axial coordination of the Thr89 hydroxyl group and the hydrogen bond between the guanidinium group of the Arg14 residue and the hydroxyl group of CuST. Furthermore, the combination of CuST with lysozyme did not decrease the superoxide dismutase activity of CuST. Based on the spectral, electrochemical, structural studies, and quantum chemical calculations, an O2 – disproportionation mechanism catalyzed by CuST@lysozyme is proposed.
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- 2023
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14. Crystal structure and Hirshfeld surface analysis of mono/bis(aqua-κO)[N-(2-oxidobenzylidene)valinato-κ3O,N,O′]copper(II): dimeric Schiff base copper(II) complexes having different numbers of coordinated water molecules
- Author
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Yukihito Akiyama, Soma Suzuki, Shintaro Suda, Yuji Takiguchi, Daisuke Nakane, and Takashiro Akitsu
- Subjects
schiff base complex ,copper ,amino acid ,hirshfeld analysis ,crystal structure ,Crystallography ,QD901-999 - Abstract
The molecular structure of the title compound, [Cu(C12H13N2O3)(H2O)2]·[Cu(C12H13N2O3)(H2O)], consists of two different molecules in the asymmetric unit. Both of the structures consist of a tridentate ligand synthesized from l-valine and salicylaldehyde, and one water molecule or two water molecules coordinating to CuII. They have a square-planar (molecule 1) or a square-pyramidal (molecule 2) coordination geometry. In the crystal, the molecules form intra- and intermolecular O—H...O hydrogen bonds involving the coordinated water molecules and other sites. A Hirshfeld surface analysis indicated that the most important contributions to the packing are from H...H [52.9% (molecule 1) and 51.1% (molecule 2)] and H...O/ O...H [21.2% (molecule 1) and 25.8% (molecule 2)] contacts. In addition, an electrostatic potential map was also obtained from DFT calculations to support the discussion of the intermolecular interactions.
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- 2023
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15. Application of Infrared Free-Electron Laser Irradiation of Protein Complexes Binding to Salen-Type Schiff Base Zn(II) Complexes Using Secondary Conformational Changes in the Proteins for the Treatment of Alzheimer’s Disease
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Hiroshi Takashima, Daisuke Nakane, and Takashiro Akitsu
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IR-FEL ,complex ,amyloid-β ,HSA ,zinc ,secondary structure ,Inorganic chemistry ,QD146-197 - Abstract
Alzheimer’s disease causes the destruction of cranial nerve cells and is said to be caused by neuronal cell death due to the accumulation of amyloid-β protein. One method for the treatment of Alzheimer’s disease is to reduce the toxicity of the amyloid beta protein. Among the possibilities is to reduce toxicity by changing the secondary structure of the protein. In this study, the secondary structure of the protein was verified by binding a zinc complex to the protein and irradiating it with an infrared free-electron laser (IR-FEL). By binding Salen-Type zinc complexes to human serum albumin (HSA) and irradiating it with IR-FEL, structural changes were observed in the α-helix and β-sheet, the secondary structure of HSA. In addition to researching the possibility of binding zinc complexes to small proteins, docking simulations were examined. GOLD docking simulations showed that it is possible to bind zinc complexes to lysozyme (Lyz), a small protein. These results suggest that binding zinc complexes to amyloid-β and inducing a secondary conformational change through IR-FEL irradiation could be used for the treatment of Alzheimer’s disease by making the complexes lose their toxicity.
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- 2024
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16. Towards Industrially Important Applications of Enhanced Organic Reactions by Microfluidic Systems
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Ayesha Zafar, China Takeda, Asif Manzoor, Daiki Tanaka, Masashi Kobayashi, Yoshitora Wadayama, Daisuke Nakane, Adnan Majeed, Muhammad Adnan Iqbal, and Takashiro Akitsu
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microfluidic system ,droplet synthesis ,microfluidic organic synthesis ,organic compounds ,Organic chemistry ,QD241-441 - Abstract
This review presents a comprehensive evaluation for the manufacture of organic molecules via efficient microfluidic synthesis. Microfluidic systems provide considerably higher control over the growth, nucleation, and reaction conditions compared with traditional large-scale synthetic methods. Microfluidic synthesis has become a crucial technique for the quick, affordable, and efficient manufacture of organic and organometallic compounds with complicated characteristics and functions. Therefore, a unique, straightforward flow synthetic methodology can be developed to conduct organic syntheses and improve their efficiency.
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- 2024
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17. Recent Advances in Chiral Schiff Base Compounds in 2023
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China Takeda, Daisuke Nakane, and Takashiro Akitsu
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n/a ,Organic chemistry ,QD241-441 - Abstract
Schiff bases (imine or azomethine –N=CH–), which were first obtained by a German chemist, H [...]
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- 2023
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18. Category Theory in Chemistry
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Takashiro Akitsu
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n/a ,Physics ,QC1-999 ,Physical and theoretical chemistry ,QD450-801 - Abstract
“Mathematical chemistry” as an academic field is said to have been proposed by Weyl in the 20th century as a way of thinking that abstracts and expresses “variables”, “symbols” and “functions” [...]
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- 2023
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19. Mathematical Geometry and Groups for Low-Symmetry Metal Complex Systems
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Takashiro Akitsu
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geometry ,group theory ,crystal structure ,low symmetry ,coordination chemistry ,Organic chemistry ,QD241-441 - Abstract
Since chemistry, materials science, and crystallography deal with three-dimensional structures, they use mathematics such as geometry and symmetry. In recent years, the application of topology and mathematics to material design has yielded remarkable results. It can also be seen that differential geometry has been applied to various fields of chemistry for a relatively long time. There is also the possibility of using new mathematics, such as the crystal structure database, which represents big data, for computational chemistry (Hirshfeld surface analysis). On the other hand, group theory (space group and point group) is useful for crystal structures, including determining their electronic properties and the symmetries of molecules with relatively high symmetry. However, these strengths are not exhibited in the low-symmetry molecules that are actually handled. A new use of mathematics for chemical research is required that is suitable for the age when computational chemistry and artificial intelligence can be used.
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- 2023
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20. Efficient Synthesis of a Schiff Base Copper(II) Complex Using a Microfluidic Device
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Masashi Kobayashi, Takashiro Akitsu, Masahiro Furuya, Tetsushi Sekiguchi, Shuichi Shoji, Takashi Tanii, and Daiki Tanaka
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Schiff base ,copper complex ,microfluidic ,high throughput ,Mechanical engineering and machinery ,TJ1-1570 - Abstract
The efficient synthesis of amino acid Schiff base copper(II) complexes using a microfluidic device was successfully achieved. Schiff bases and their complexes are remarkable compounds due to their high biological activity and catalytic function. Conventionally, products are synthesized under reaction conditions of 40 °C for 4 h using a beaker-based method. However, in this paper, we propose using a microfluidic channel to enable quasi-instantaneous synthesis at room temperature (23 °C). The products were characterized using UV–Vis, FT–IR, and MS spectroscopy. The efficient generation of compounds using microfluidic channels has the potential to significantly contribute to the efficiency of drug discovery and material development due to high reactivity.
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- 2023
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21. Chiral crystallization of a zinc(II) complex
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Shabana Noor, Shintaro Suda, Tomoyuki Haraguchi, Fehmeeda Khatoon, and Takashiro Akitsu
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chiral crystallization ,zinc(ii) ,hirshfeld analysis ,crystal structure ,Crystallography ,QD901-999 - Abstract
The compound, {6,6′-dimethoxy-2,2′-[(4-azaheptane-1,7-diyl)bis(nitrilomethanylidyne)]diphenolato}zinc(II) methanol monosolvate, [Zn(C22H27N3O4)]·CH3OH, at 298 K crystallizes in the orthorhombic space group Pna21. The Zn atom is coordinated by a pentadentate Schiff base ligand in a distorted trigonal–bipyramidal N3O2 geometry. The equatorial plane is formed by the two phenolic O and one amine N atom. The axial positions are occupied by two amine N atoms. The distorted bipyramidal geometry is also supported by the trigonality index (τ), which is found to be 0.85 for the molecule. In the crystal, methanol solvent molecule is connected to the complex molecule by an O—H...O hydrogen bond and the complex molecules are connected by weak supramolecular interactions, so achiral molecules generate a chiral crystal. The Hirshfeld surface analysis suggests that H...H contacts account for the largest percentage of all interactions.
- Published
- 2021
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22. Crystal structure and Hirshfeld surface analysis of ((S,S)-2,2′-{[(1,2-diphenylethane-1,2-diyl)bis[(azaniumylylidene)methanylylidene]}bis(6-methoxyphenolato))trinitratosamarium(III)
- Author
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Yuta Okumura, Yuji Takiguchi, Daisuke Nakane, and Takashiro Akitsu
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schiff base ligand ,samarium ,chirality ,hirshfeld analysis ,crystal structure ,Crystallography ,QD901-999 - Abstract
In the title complex, [Sm(NO3)3(C30H28N2O4)], the Sm atom is surrounded by ten O atoms. The (S,S)-2,2′-{[(1,2-diphenylethane-1,2-diyl)bis[(azaniumylylidene)methanylylidene]}bis(6-methoxyphenolate) ligand, obtained from o-vanillin and (1S,2S)-(−)-1,2-diphenylethylenediamine, exhibits a slightly distorted planar arrangement of the four coordinated O atoms. In the crystal, the complex shows intramolecular N—H...O hydrogen bonds and weak intermolecular C—H...O hydrogen bonds. The Hirshfeld surface analysis indicates that the most important contributions to the packing are from H...H (33.5%), O...H (34.1%) and C...H (21.7%) contacts.
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- 2021
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23. Infrared Free Electron Laser or Polarized Ultraviolet Photolysis of Hierarchical and Chiral Components of Interleukin-6, AlanylAlanine and Alanine
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Nanami Fujisawa, Yuika Onami, Takayasu Kawasaki, Tomoyuki Haraguchi, Takashiro Akitsu, and Koichi Tsukiyama
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interleukin 6 ,alanyl-alanine ,alanine ,ir-fel ,polarized light ,salam hypothesis ,Medicine ,Biology (General) ,QH301-705.5 - Abstract
Interleukin-6 (IL-6) could be decomposed by irradiation of IR-FEL (Infrared free electron laser). Using circularly polarized and other UV light and IR-FEL light, photolysis of hierarchical components of cast films of IL-6, namely deuterated aqueous solutions of enantiomers of dipeptide (L-alanyl-L-alanine (Ala-ala) or D-alanyl-D-alanine) and enantiomers of amino acid (L-alanine (Ala) or D-alanine) was investigated whether specific bonds can be broken by absorption of light (not due to heat). In addition, IR-FEL irradiation to powder as well as crystal structure determination for L-Ala and D-Ala at 173 and 293 K were also carried out to confirm reproducibility in the solid state about long-lasting controversy about Salam’ hypothesis associated with chirality exhibiting structural phase transition at different temperature. Subunits of IL-6 (dipeptide and amino acid) could not be decomposed by polarized IR-FEL nor UV (ultraviolet) light regardless of their chirality. All experimental methods tested in this study failed to prove Salam's hypothesis, positively. Consequently, secondary structure of IL-6 was found to be easier to be damaged by IR-FEL than covalent bonds. HIGHLIGHTS • Interleukin 6 (IL-6) was decomposed by irradiation of IR-FEL (Infrared free electron laser). • Parts of IL-6 (dipeptide and amino acid) was not decomposed by polarized IR-FEL nor UV (ultraviolet) light regardless of their chirality. • Secondary structure of IL-6 was easier to be damaged by IR-FEL than covalent bonds.
- Published
- 2021
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24. Crystal structure and Hirshfeld surface analysis of (aqua-κO)(methanol-κO)[N-(2-oxidobenzylidene)threoninato-κ3O,N,O′]copper(II)
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Natsuki Katsuumi, Yuika Onami, Sayantan Pradhan, Tomoyuki Haraguchi, and Takashiro Akitsu
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schiff base complex ,copper ,amino acid ,hirshfeld analysis ,crystal structure ,Crystallography ,QD901-999 - Abstract
In the title complex molecule, [Cu(C11H11NO4)(CH4O)(H2O)], the Cu atom is coordinated in a distorted square-pyramidal geometry by a tridentate ligand synthesized from l-threonine and salicylaldehyde, one methanol molecule and one water molecule. In the crystal, the molecules show intra- and intermolecular O—H...O hydrogen bonds. The Hirshfeld surface analysis indicates that the most important contributions to the packing are H...H (49.4%) and H...O/O...H (31.3%) contacts.
- Published
- 2020
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25. Lanthanide Complexes in Recent Molecules
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Takashiro Akitsu
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n/a ,Organic chemistry ,QD241-441 - Abstract
The MDPI journal Molecules publishes excellent papers on molecules in every issue, but I found that there are surprisingly only a few papers (3) and reviews (1) on rare-earth elements (lanthanide) in the category of inorganic chemistry these days [...]
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- 2022
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26. Photofunctions in Hybrid Systems of Schiff Base Metal Complexes and Metal or Semiconductor (Nano)Materials
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Takashiro Akitsu, Barbara Miroslaw, and Shanmugavel Sudarsan
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photofunction ,Schiff base ,metal complex ,photocatalysts ,semiconductors ,nanomaterials ,Biology (General) ,QH301-705.5 ,Chemistry ,QD1-999 - Abstract
Composite materials very often provide new catalytic, optical or other physicochemical properties not observed for each component separately. Photofunctions in hybrid systems are an interesting topic of great importance for industry. This review presents the recent advances, trends and possible applications of photofunctions of hybrid systems composed of Schiff base metal complexes and metal or semiconductor (nano)materials. We focus on photocatalysis, sensitization in solar cells (DSSC—dye sensitized solar cell), ligand-induced chirality and applications in environmental protection for Cr(VI) to Cr(III) reduction, in cosmetology as sunscreens, in real-time visualization of cellular processes, in bio-labeling, and in light activated prodrug applications.
- Published
- 2022
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27. Symmetry in Organic/Inorganic Hybrid Materials
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Takashiro Akitsu
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n/a ,Mathematics ,QA1-939 - Abstract
The term “organic/inorganic hybrid materials” here refers to a metal complex consisting of an inorganic metal ion and an organic ligand, a metalloprotein, or a composite functional material in which an inorganic compound and an organic material are combined (Figure 1) [...]
- Published
- 2022
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28. Synthesis and structural study of tris(2,6-diaminopyridinium) bis(oxalato)dioxidovanadate(V) 2.5-hydrate
- Author
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Hiba Sehimi, Takashiro Akitsu, and Mohamed Faouzi Zid
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crystal structure ,vanadium ,bis(oxalato) complexes ,dioxovanadate(V) ,2,6-diaminopyridine ,Crystallography ,QD901-999 - Abstract
Crystals of the title compound, (C5H8N3)3[VO2(C2O4)2]·2.5H2O, a mononuclear VV complex, were obtained by slow evaporation at room temperature of an aqueous solution containing vanadium pentoxide, oxalic acid and 2,6-diaminopyridine. The asymmetric unit contains one bis(oxalato)dioxovanadate(V) anionic complex, three 2,6-diaminopyridinium cations and two and a half uncoordinated water molecules. The mononuclear vanadium(V) anions are connected to the organic cations and water molecules through a strong N—H...O and O—H...O hydrogen-bond network, consolidated by π–π stacking interactions, to form a three-dimensional structure.
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- 2019
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29. Three closely related 1-[(1,3-benzodioxol-5-yl)methyl]-4-(halobenzoyl)piperazines: similar molecular structures but different intermolecular interactions
- Author
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Ninganayaka Mahesha, Belakavadi K. Sagar, Hemmige S. Yathirajan, Tetsundo Furuya, Tomoyuki Haraguchi, Takashiro Akitsu, and Christopher Glidewell
- Subjects
piperazines ,crystal structure ,molecular conformation ,hydrogen bonding ,supramolecular assembly ,Crystallography ,QD901-999 - Abstract
In each of the compounds 1-[(1,3-benzodioxol-5-yl)methyl]-4-(3-fluorobenzoyl)piperazine, C19H19FN2O3 (I), 1-[(1,3-benzodioxol-5-yl)methyl]-4-(2,6-difluorobenzoyl)piperazine, C19H18F2N2O3 (II), and 1-[(1,3-benzodioxol-5-yl)methyl]-4-(2,4-dichlorobenzoyl)piperazine, C19H19Cl2N2O3 (III), the piperazine rings adopt a chair conformation with the (1,3-benzodioxol-5-yl)methyl substituent occupying an equatorial site: the five-membered rings are all slightly folded across the O...O line leading to envelope conformations. The dihedral angle between the planar amidic fragment and the haloaryl ring is 62.97 (5)° in (I) but 77.72 (12)° and 75.50 (5)° in (II) and (III), respectively. Despite their similarity in constitution and conformation, the supramolecular interactions in (I)–(III) differ: in (I), a combination of C—H...O and C—H...π(arene) hydrogen bonds links the molecules into a three-dimensional framework structure, but there are no hydrogen bonds of any sort in either (II) or (III), although the structure of (III) contains a short Cl...Cl contact between inversion-related pairs of molecules.
- Published
- 2019
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30. Co-crystallization of 3,5-dinitrobenzoic acid with two antipsychotic agents: a simple 1:1 salt with trihexyphenidyl and a 1:2 acid salt containing a very short O—H...O hydrogen bond with chlorprothixene
- Author
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Mohammed A. E. Shaibah, Hemmige S. Yathirajan, Ravindranath S. Rathore, Tetsundo Furuya, Tomoyuki Haraguchi, Takashiro Akitsu, and Christopher Glidewell
- Subjects
co-crystallization ,acid salts ,crystal structure ,molecular conformation ,hydrogen bonding ,supramolecular assembly ,Crystallography ,QD901-999 - Abstract
Co-crystallization of racemic 1-cyclohexyl-1-phenyl-3-(piperidin-1-yl)propan-1-ol (trihexyphenidyl) with 3,5-dinitrobenzoic acid gives a simple 1:1 salt, namely 1-(3-cyclohexyl-3-hydroxy-3-phenylpropyl)piperidin-1-ium 3,5-dinitrobenzoate, C20H32NO+·C7H3N2O6−, (I), whereas a similar co-crystallization using (Z)-3-(2-chloro-9H-thioxanthen-9-yl)-N,N-dimethylpropan-1-amine (chlorprothixene) gives a 1:2 acid salt, namely (Z)-3-(2-chloro-9H-thioxanthen-9-yl)-N,N-dimethylpropan-1-aminium hydrogen bis(3,5-dinitrobenzoate), C18H19ClNS+·[H(C7H3N2O6)2]−, (II), the anion of which contains a very short O—H...O hydrogen bond, with dimensions O—H = 1.04 (3) Å, H...O = 1.41 (3) Å, O...O = 2.4197 (15) Å and O—H...O = 161 (3)°. In the cation of (I), the cyclohexyl and piperidyl rings both adopt chair conformations, whereas in the cation of (II), the central heterocyclic ring adopts a boat conformation, so that the dihedral angle between the two aryl rings is 41.56 (4)°. A combination of O—H...O, N—H...O and C—H...O hydrogen bonds links the ions of (I) into a complex chain of rings, and these chains are linked into sheets by π–π stacking interactions between inversion-related pairs of anions. In compound (II), a different combination of O—H...O, N—H...O and C—H...O hydrogen bonds links the ions into sheets. Comparisons are made with some related structures.
- Published
- 2019
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31. The crystal structure of 1-(2-iodobenzoyl)-4-(pyrimidin-2-yl)piperazine: a three-dimensional hydrogen-bonded framework, augmented by π–π stacking interactions and I...N halogen bonds
- Author
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Ninganayaka Mahesha, Hemmige S. Yathirajan, Tetsundo Furuya, Takashiro Akitsu, and Christopher Glidewell
- Subjects
pyrimidine ,piperazine ,crystal structure ,molecular conformation ,hydrogen bonding ,supramolecular assembly ,Crystallography ,QD901-999 - Abstract
In 1-(2-iodobenzoyl)-4-(pyrimidin-2-yl)piperazine, C15H15IN4O, the central piperazine ring adopts an almost perfect chair conformation with the pyrimidine substituent in an equatorial site. The planar amide unit makes a dihedral angle of 80.44 (7)° with the phenyl ring. A combination of C—H...O and C—H...π(arene) hydrogen bonds links the molecules into a complex three-dimensional network structure, augmented by a π–π stacking interaction and an I...N halogen bond, all involving different pairs of inversion-related molecules. Comparisons are made with the structures of a number of related compounds.
- Published
- 2019
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32. The Effect of AlI3 Nanoadditive on the Thermal Behavior of PMMA Subjected to Thermoanalytical Py-GC-MS Technique
- Author
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Muhammad Adnan, Taj Ur Rahman, Ali Bahadur, Muhammad Aurang Zeb, Wajiha Liaqat, Takashiro Akitsu, Shams H. Abdel-Hafez, and Wael A. El-Sayed
- Subjects
PMMA ,aluminum triiodide ,thermoanalytical study ,degradation ,Technology ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Microscopy ,QH201-278.5 ,Descriptive and experimental mechanics ,QC120-168.85 - Abstract
Thermal degradation of polymethylmethacrylate (PMMA) was studied by using inorganic salt of aluminum triiodide (AlI3). The composites of PMMA were prepared with AlI3 by changing the concentration of the AlI3 additive from 2% to 10% (w/w). The PMMA composites with AlI3 were characterized by TGA, DTG, SEM, FTIR, HBT, and Py-GC-MS techniques. The FTIR peaks of PMMA composite at 1316, 786, and 693 cm−1 justify the chemical association between PMMA and AlI3. TGA study shows that the stability of PMMA is enhanced by the addition of the AlI3 additive. SEM analysis represented that there is a relationship between polymer and additive when they are mixed at the molecular level. The horizontal burning test (HBT) also confirmed that the AlI3 additive produced the flame retarding properties in PMMA polymer. The burning rate of composite with 10% of AlI3 additive decreases five times as much as compared to pure PMMA polymer. Py-GC-MS analysis deduced that PMMA composite produced less toxic and environment-friendly substances (CO2) by the influence of AlI3 additive as compared to neat PMMA.
- Published
- 2021
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33. Crystal structure of (E)-3-[(2,6-dimethylphenyl)diazenyl]-7-methyl-1H-indazole
- Author
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Shiomi Yagi, Tomoyuki Haraguchi, and Takashiro Akitsu
- Subjects
crystal structure ,photochromism ,azo benzene ,pyrazole ,indazole ,chiral crystallization ,Crystallography ,QD901-999 - Abstract
The title azo compound, C16H16N4, was synthesized from 2,6-dimethylaniline. The diazenyl group adopts a trans (E) conformation, with an N=N bond length of 1.265 (4) Å. The pyrazole ring is approximately planar. In the crystal, zigzag chains along the b-axis direction with a C(3) is graph-set motif are formed by N—H...N hydrogen bonds involving the pyrazole moiety.
- Published
- 2018
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- View/download PDF
34. Crystal structure of 3,6-dihydroxy-4,5-dimethylbenzene-1,2-dicarbaldehyde
- Author
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Shu Yamazaki, Kazuki Nishiyama, Shiomi Yagi, Tomoyuki Haraguchi, and Takashiro Akitsu
- Subjects
crystal structure ,alkylating agents ,chiral crystallization ,Crystallography ,QD901-999 - Abstract
The title compound, C10H10O4, was synthesized from tetramethyl-1,4-benzoquinone. In the crystal, the almost planar molecule (r.m.s. deviation = 0.024 Å) forms intramolecular hydrogen bonds between the aldehyde and hydroxy groups and exhibits C2v symmetry. This achiral molecule crystallizes in the chiral space group P21 with intermolecular O—H...O and C—H...O hydrogen bonding and C—H...π and C=O...π interactions stabilizing the crystal packing.
- Published
- 2018
- Full Text
- View/download PDF
35. Towards New Chiroptical Transitions Based on Thought Experiments and Hypothesis
- Author
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Takashiro Akitsu, Sanyobi Kim, and Daisuke Nakane
- Subjects
supramolecular chirality ,DFT ,circular dichroism ,transition ,angular momentum ,Mathematics ,QA1-939 - Abstract
We studied supramolecular chirality induced by circularly polarized light. Photoresponsive azopolymers form a helical intermolecular network. Furthermore, studies on photochemical materials using optical vortex light will also attract attention in the future. In contrast to circularly polarized light carrying spin angular momentum, an optical vortex with a spiral wave front and carrying orbital angular momentum may impart torque upon irradiated materials. In this review, we summarize a few examples, and then theoretically and computationally deduce the differences in spin angular momentum and orbital angular momentum depending on molecular orientation not on, but in, polymer films. UV-vis absorption and circular dichroism (CD) spectra are consequences of electric dipole transition and magnetic dipole transition, respectively. However, the basic effect of vortex light is postulated to originate from quadrupole transition. Therefore, we explored the simulated CD spectra of azo dyes with the aid of conventional density functional theory (DFT) calculations and preliminary theoretical discussions of the transition of CD. Either linearly or circularly polarized UV light causes the trans–cis photoisomerization of azo dyes, leading to anisotropic and/or helically organized methyl orange, respectively, which may be detectable by CD spectroscopy after some technical treatments. Our preliminary theoretical results may be useful for future experiments on the irradiation of UV light under vortex.
- Published
- 2021
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- View/download PDF
36. Crystal structure of bis[cis-(1,4,8,11-tetraazacyclotetradecane-κ4N)bis(thiocyanato-κN)chromium(III)] dichromate monohydrate from synchrotron X-ray diffraction data
- Author
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Dohyun Moon, Masahiro Takase, Takashiro Akitsu, and Jong-Ha Choi
- Subjects
crystal structure ,cyclam ,chromium(III) complex ,thiocyanate ligand ,cis-V conformation ,dichromate anion ,hydrogen bonding ,synchrotron radiation ,Crystallography ,QD901-999 - Abstract
The structure of the complex salt, cis-[Cr(NCS)2(cyclam)]2[Cr2O7]·H2O (cyclam = 1,4,8,11-tetraazacyclotetradecane, C10H24N4), has been determined from synchrotron data. The asymmetric unit comprises of one [Cr(NCS)2(cyclam)]+ cation, one half of a Cr2O72− anion (completed by inversion symmetry) and one half of a water molecule (completed by twofold rotation symmetry). The CrIII ion is coordinated by the four cyclam N atoms and by two N atoms of cis-arranged thiocyanate anions, displaying a distorted octahedral coordination sphere. The Cr—N(cyclam) bond lengths are in the range 2.080 (2) to 2.097 (2) Å while the average Cr—N(NCS) bond length is 1.985 (4) Å. The macrocyclic cyclam moiety adopts the cis-V conformation. The bridging O atom of the dichromate anion is disordered around an inversion centre, leading to a bending of the Cr—O—Cr bridging angle [157.7 (3)°]; the anion has a staggered conformation. The crystal structure is stabilized by intermolecular hydrogen bonds involving the cyclam N—H groups and water O—H groups as donor groups, and the O atoms of the Cr2O72− anion and water molecules as acceptor groups, giving rise to a three-dimensional network.
- Published
- 2017
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37. (Z)-1-Benzoyl-5-benzylidene-2-hydroxy-4-oxo-4,5-dihydro-1H-pyrrole-3-carbonitrile
- Author
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Yuika Onami, Budanur P. Siddaraju, Haleyur G. Anilkumar, Hemmige S. Yathirajan, Tomoyuki Haraguchi, and Takashiro Akitsu
- Subjects
crystal structure ,pyrrole ,heterocycle ,phenyl group ,chiral crystallization ,Crystallography ,QD901-999 - Abstract
The title compound, C19H12N2O3, obtained as an intermediate in the synthesis of a pyrrole derivative, is composed of a five-membered heterocycle with substituted groups via double or triple bonds as well as single bonds, without an asymmetric carbon atom. An intramolecular O—H...O link occurs. In the crystal, O—H...N hydrogen bonds link the molecules.
- Published
- 2019
- Full Text
- View/download PDF
38. Methyl 1-methyl-1H-indole-3-carboxylate
- Author
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Tetsundo Furuya, Shiomi Yagi, Shu Yamazaki, Tomoyuki Haraguchi, Takashiro Akitsu, Ninganayaka Mahesha, Belakavadi K. Sagar, and Hemmige S. Yathirajan
- Subjects
indole ,crystal structure ,carboxylate ,hydrogen bonding ,coplanar ,Crystallography ,QD901-999 - Abstract
The title indole derivative, C11H11NO2, was synthesized from 1-methyl-1H-indole-3-carboxylic acid and methanol. The molecule is planar as it is situated on a mirror plane present in the space group Pbcm. In the crystal, molecules form three kinds of intermolecular C—H...O hydrogen bonds, resulting in a sheet structure in the ab plane. Parallel sheets interact by C—H...π stacking, stabilizing the crystal packing.
- Published
- 2018
- Full Text
- View/download PDF
39. Crystallographic and Computational Electron Density of dx2-y2 Orbitals of Azo-Schiff Base Metal Complexes Using Conventional Programs
- Author
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Yuji Takiguchi, Yuika Onami, Tomoyuki Haraguchi, and Takashiro Akitsu
- Subjects
Schiff base ,metal complex ,electron density ,coordination bond ,DFT ,Organic chemistry ,QD241-441 - Abstract
The crystal structures of two azobenzene derivative Schiff base metal complexes (new C44H40CuN6O2 of P-1 and known C44H38MnN6O7 of P21/c abbreviated as Cu and Mn, respectively) were (re-)determined experimentally using conventional X-ray analysis to obtain electron density using a PLATON program. Cu affords a four-coordinated square planar geometry, while Mn affords a hexa-coordinated distorted octahedral geometry whose apical sites are occupied by an acetate ion and water ligands, which are associated with hydrogen bonds. The π-π or CH-π and hydrogen bonding intermolecular interactions were found in both crystals, which were also analyzed using a Hirshfeld surface analysis program. To compare these results with experimental results, a density functional theory (DFT) calculation was also carried out based on the crystal structures to obtain calculated electron density using a conventional Gaussian program. These results revealed that the axial Mn-O coordination bonds of Mn were relatively weaker than the in-plane M-N or M-O coordination bonds.
- Published
- 2021
- Full Text
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40. Success or Failure of Chiral Crystallization of Similar Heterocyclic Compounds
- Author
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Cyprian M. Chunkang, Iris E. Ikome, Emmanuel N. Nfor, Yuta Mitani, Natsuki Katsuumi, Tomoyuki Haraguchi, and Takashiro Akitsu
- Subjects
heterocycle compound ,chiral crystallization ,crystal structure ,space group ,hydrogen bonds ,Organic chemistry ,QD241-441 - Abstract
Single crystals of two achiral and planar heterocyclic compounds, C9H8H3O(CA1) and C8H5NO2 (CA4), recrystallized from ethanol, were characterized by single crystal X-ray analysis, respectively, and chiral crystallization was observed only for CA1 as P212121 (# 19), whereas it was not observed for CA4P21/c (# 14). In CA1, as a monohydrate, the hydrogen bonds were pronounced around the water of crystallization (O4), and the planar cyclic sites were arranged in parallel to slightly tilted positions. On the other hand, an anhydride CA4 formed a dimer by hydrogen bonds between adjacent molecules in the crystal, which were aggregated by van der Waals forces and placed in parallel planar cyclic sites.
- Published
- 2020
- Full Text
- View/download PDF
41. Development of Microdroplet Generation Method for Organic Solvents Used in Chemical Synthesis
- Author
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Shohei Hattori, Chenghe Tang, Daiki Tanaka, Dong Hyun Yoon, Yoshito Nozaki, Hiroyuki Fujita, Takashiro Akitsu, Tetsushi Sekiguchi, and Shuichi Shoji
- Subjects
microfluidics ,microdroplets ,organic solvents ,organic droplets ,Organic chemistry ,QD241-441 - Abstract
Recently, chemical operations with microfluidic devices, especially droplet-based operations, have attracted considerable attention because they can provide an isolated small-volume reaction field. However, analysis of these operations has been limited mostly to aqueous-phase reactions in water droplets due to device material restrictions. In this study, we have successfully demonstrated droplet formation of five common organic solvents frequently used in chemical synthesis by using a simple silicon/glass-based microfluidic device. When an immiscible liquid with surfactant was used as the continuous phase, the organic solvent formed droplets similar to water-in-oil droplets in the device. In contrast to conventional microfluidic devices composed of resins, which are susceptible to swelling in organic solvents, the developed microfluidic device did not undergo swelling owing to the high chemical resistance of the constituent materials. Therefore, the device has potential applications for various chemical reactions involving organic solvents. Furthermore, this droplet generation device enabled control of droplet size by adjusting the liquid flow rate. The droplet generation method proposed in this work will contribute to the study of organic reactions in microdroplets and will be useful for evaluating scaling effects in various chemical reactions.
- Published
- 2020
- Full Text
- View/download PDF
42. Crystal structure of hexakis(urea-κO)chromium(III) dichromate bromide monohydrate from synchrotron X-ray data
- Author
-
Dohyun Moon, Shinnosuke Tanaka, Takashiro Akitsu, and Jong-Ha Choi
- Subjects
crystal structure ,chromium(III) complex ,urea ligand ,bromide salt ,hydrogen bonding ,synchrotron data ,Crystallography ,QD901-999 - Abstract
The title bromide salt, [Cr{CO(NH2)2}6](Cr2O7)Br·H2O, is isotypic to the corresponding chloride salt. Within the complex cation, the CrIII atom is coordinated by six O atoms of six urea ligands, displaying a slightly distorted octahedral coordination environment. The Cr—O bond lengths involving the urea ligands are in the range 1.9534 (13)–1.9776 (12) Å. The Cr2O72− anion has a nearly staggered conformation, with a bridging angle of 130.26 (10)°. The individual components are arranged in rows extending parallel to [100]. The Br− anion links the complex cation, as well as the solvent water molecule, through N—H...Br and O—H...Br hydrogen-bonding interactions. The supramolecular architecture also includes N—H...O and O—H...O hydrogen bonding between urea N—H and water O—H donor groups and the O atoms of the Cr2O72− anion as acceptor atoms, leading to a three-dimensional network structure.
- Published
- 2015
- Full Text
- View/download PDF
43. Electron Transfer via Helical Oligopeptide to Laccase Including Chiral Schiff Base Copper Mediators
- Author
-
Kumpei Kashiwagi, Francesco Tassinari, Tomoyuki Haraguchi, Koyel Banerjee-Gosh, Takashiro Akitsu, and Ron Naaman
- Subjects
chirality ,oligopeptide ,laccase ,copper complex ,electron transfer ,Mathematics ,QA1-939 - Abstract
The oxygen reduction efficiency of a laccase-modified electrode was found to depend on the chirality of the oligopeptide linker used to bind the enzyme to the surface. At the same time, the electron transfer between the cathode electrode and the enzyme is improved by using a copper(II) complex with amino-acid derivative Schiff base ligand with/without azobenzene moiety as a mediator. The increased electrochemical current under both O2 and N2 proves that both the mediators are active towards the enzyme.
- Published
- 2020
- Full Text
- View/download PDF
44. Photo-Tunable Azobenzene-Anthraquinone Schiff Base Copper Complexes as Mediators for Laccase in Biofuel Cell Cathode
- Author
-
Kazuto Kajiwara, Sayantan Pradhan, Tomoyuki Haraguchi, Chittaranjan Sinha, Rakesh Parida, Santanab Giri, Gourisankar Roymahaptra, and Takashiro Akitsu
- Subjects
enzymatic fuel cells ,laccase ,salen Cu(II) complex ,docking ,mediator ,photo-tuning ,Mathematics ,QA1-939 - Abstract
Induced chirality (achiral target in chiral matrix such as proteins) sometimes play a useful role in evaluating supramolecular systems involving biomolecules. Enzymatic fuel cells, which generate electricity via enzymatic redox reactions at electrodes hold a significant potential for sustainable power. Bacterial laccase, a multi-copper oxidase, was used in the cathodic compartment of the enzymatic biofuel cells because of its low redox potential. Three new salen Cu(II) complexes were designed and investigated as mediators. The Schiff base ligands consisted of both a redox-active (anthraquinone) and a photochromic (azobenzene) moiety. The interaction between laccase and a mediator was examined with induced circular dichroism (CD) and the docking tool to observe in which of the laccase domains the mediators bind as well as study the photo-induced tuning of both the cis-trans photoisomerization and orientation by the Weigert effect. Both the electrochemical and photochromic properties are also discussed and compared using density functional theory (DFT), time-dependent (TD)-DFT, and docking simulations.
- Published
- 2020
- Full Text
- View/download PDF
45. Degradation of Human Serum Albumin by Infrared Free Electron Laser Enhanced by Inclusion of a Salen-Type Schiff Base Zn (II) Complex
- Author
-
Yuika Onami, Takayasu Kawasaki, Hiroki Aizawa, Tomoyuki Haraguchi, Takashiro Akitsu, Koichi Tsukiyama, and Mauricio A. Palafox
- Subjects
ir-fel ,human serum albumin ,schiff base ,zn(ii) complex ,td-dft ,fluorescence ,Biology (General) ,QH301-705.5 ,Chemistry ,QD1-999 - Abstract
A salen-type Schiff base Zn(II) complex included in human serum albumin (HSA) protein was examined by UV-Vis, circular dichroism (CD), and fluorescence (PL) spectra. The formation of the composite material was also estimated by a GOLD program of ligand−protein docking simulation. A composite cast film of HSA and Zn(II) complex was prepared, and the effects of the docking of the metal complex on the degradation of protein molecules by mid-infrared free electron laser (IR-FEL) were investigated. The optimum wavelengths of IR-FEL irradiation to be used were based on experimental FT-IR spectra and vibrational analysis. Using TD-DFT results with 6-31G(d,p) and B3LYP, the IR spectrum of Zn(II) complex could be reasonably assigned. The respective wavelengths were 1652 cm−1 (HSA amide I), 1537 cm−1 (HSA amide II), and 1622 cm−1 (Zn(II) complex C=N). Degradation of HSA based on FT-IR microscope (IRM) analysis and protein secondary structure analysis program (IR-SSE) revealed that the composite material was degraded more than pure HSA or Zn(II) complex; the inclusion of Zn(II) complex enhanced destabilization of folding of HSA.
- Published
- 2020
- Full Text
- View/download PDF
46. Orientation of Chiral Schiff Base Metal Complexes Involving Azo-Groups for Induced CD on Gold Nanoparticles by Polarized UV Light Irradiation
- Author
-
Nobumitsu Sunaga, Tomoyuki Haraguchi, and Takashiro Akitsu
- Subjects
chirality ,azobenzene ,photo-isomerization ,Weigert effect ,Schiff base complexes ,gold nanoparticles ,time-dependent density functional theory (TD-DFT) ,Mathematics ,QA1-939 - Abstract
In this study, we report the synthesis, characterization, and chiroptical properties of azo-group-containing chiral salen type Schiff base Ni(II), Cu(II), and Zn(II) complexes absorbed on gold nanoparticles (AuNPs) of 10 nm diameters. Induced circular dichroism (CD) around the plasmon region from the chiral species weakly adsorbed on the surface of AuNP were observed when there were appropriate dipole−dipole interactions at the initial states. Spectral changes were also observed by not only cis-trans photoisomerization of azo-groups but also changes of orientation due to Weigert effect of azo-dyes after linearly polarized UV light irradiation. Spatial features were discussed based on dipole-dipole interactions mainly within an exciton framework.
- Published
- 2019
- Full Text
- View/download PDF
47. Potassium 3-formyl-[1,1′-biphenyl]-4-olate monohydrate
- Author
-
Ryoji Moriwaki, Tomoyuki Haraguchi, and Takashiro Akitsu
- Subjects
crystal structure ,cross coupling reactions ,potassium cation ,Crystallography ,QD901-999 - Abstract
The title salt, K+·C13H9O2−·H2O, was synthesized from 5-bromosalicylaldehyde and a phenylboronic acid derivative using the Suzuki–Miyaura cross-coupling reaction (Miyaura & Suzuki, 1979). In addition to the intermolecular interactions between the charged species, two O—H...O hydrogen bonds involving the isolated water molecules further stabilize the crystal packing of the title salt leading to the formation of a three-dimensional framework structure.
- Published
- 2017
- Full Text
- View/download PDF
48. Multifunctional Composites of Chiral Valine Derivative Schiff Base Cu(II) Complexes and TiO2
- Author
-
Yuki Takeshita, Kazuya Takakura, and Takashiro Akitsu
- Subjects
Schiff base complexes ,copper(II) complexes ,UV–Vis spectra ,TD-DFT ,TiO2 ,Biology (General) ,QH301-705.5 ,Chemistry ,QD1-999 - Abstract
We have prepared four new Cu(II) complexes containing valine moieties with imidazole ligands at the fourth coordination sites and examined their photo-induced reactions with TiO2 in order of understanding the reaction mechanisms. Under a nitrogen atmosphere, the intermolecular electron transfer reactions (essentially supramolecular interactions) of these systems, which resulted in the reduction of Cu(II) species to Cu(I) ones, occurred after UV light irradiation. In this study, we have investigated the conditions of the redox reactions in view of substituent effects of aldehyde moieties. The results of cyclic voltammetry (CV) on an rotating ring-disk electrode (RRDE) suggested that the substitution effects and redox potentials were correlated. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were also performed to simulate the UV–Vis and circular dichroism (CD) spectra; the results revealed a reasonably good correlation between the substituent effects and the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals (HOMO-LUMO) gaps associated with the most intense transition bands. In addition, we summarized the substitution effects of Cu(II) complexes for their corresponding UV light-induced reactions.
- Published
- 2015
- Full Text
- View/download PDF
49. Investigation by DFT Methods of the Damage of Human Serum Albumin Including Amino Acid Derivative Schiff Base Zn(II) Complexes by IR-FEL Irradiation
- Author
-
Yuika Onami, Ryousuke Koya, Takayasu Kawasaki, Hiroki Aizawa, Ryo Nakagame, Yoshito Miyagawa, Tomoyuki Haraguchi, Takashiro Akitsu, Koichi Tsukiyama, and Mauricio A. Palafox
- Subjects
TD-DFT ,IR-FEL ,human serum albumin ,amino acid derivative ,Schiff base ,Zn(II) complex ,Biology (General) ,QH301-705.5 ,Chemistry ,QD1-999 - Abstract
An infrared free electron laser (IR-FEL) can decompose aggregated proteins by excitation of vibrational bands. In this study, we prepared hybrid materials of protein (human serum albumin; HSA) including several new Schiff base Zn(II) complexes incorporating amino acid (alanine and valine) or dipeptide (gly-gly) derivative moieties, which were synthesized and characterized with UV-vis, circular dichroism (CD), and IR spectra. Density functional theory (DFT) and time dependent DFT (TD-DFT) calculations were also performed to investigate vibrational modes of the Zn(II) complexes. An IR-FEL was used to irradiate HSA as well as hybrid materials of HSA-Zn(II) complexes at wavelengths corresponding to imine C=N, amide I, and amide II bands. Analysis of secondary structures suggested that including a Zn(II) complex into HSA led to the structural change of HSA, resulting in a more fragile structure than the original HSA. The result was one of the characteristic features of vibrational excitation of IR-FEL in contrast to electronic excitation by UV or visible light.
- Published
- 2019
- Full Text
- View/download PDF
50. Chiral Recognition of Azo-Schiff Base Ligands, Their Cu(II) Complexes, and Their Docking to Laccase as Mediators
- Author
-
Fuki Kunitake, Jong-Yeon Kim, Shiomi Yagi, Shu Yamzaki, Tomoyuki Haraguchi, and Takashiro Akitsu
- Subjects
chiral Schiff base ,spontaneous resolution ,enantiomer ,diastereomer ,azobenzene ,Weigert effect ,copper(II) (Cu(II)) complex ,laccase ,Mathematics ,QA1-939 - Abstract
Chiral crystals were discovered due to spontaneous resolution when enantiomers of 4-phenyldiazenyl-2-[(R or S)-(1-phenylethyl)-iminomethyl]phenol and its racemic mixture were prepared. Using two ligands per molecule, optically active R,R and S,S enantiomers and meso R,S diastereomer of Cu(II) complexes were prepared. Strong chiral recognition was expected for them. Laccase has attracted attention as a catalyst that reduces oxygen to water in a cathode of biofuel cells, which can be effectively mediated by metal complexes. Furthermore, azobenzene can align perpendicularly to the polarization direction of irradiating linearly polarized ultraviolet light (Weigert effect) as well as to the conventional cis-trans photoisomerization accompanying the shift of redox potential. Thus, we also studied the photo-induced control of cis-trans forms and the alignment of these Cu(II) complexes as a mediator to fit laccase appropriately. We discuss photo-induced control on not only electronically but also sterically-favored redox conditions. The meso(R,S)-form of the Cu(II) complex in cis-form was found to be the best at increasing the current of cyclic voltammetry (CV) among the three R,R and S,S enantiomers and the R,S diastereomer of the Cu(II) complexes.
- Published
- 2019
- Full Text
- View/download PDF
Catalog
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